This guide provides finishers an overview of cleaners, the differences between them and discusses what to look for in choosing an effective alkaline cleaner. Alkaline cleaning blends alkalinity sources with a balanced amount of surfactants to constitute a highly effective metal cleaner. The concentrate is dissolved in water and, in combination with mechanical action and temperature, generally removes most contaminants. This method is cost-effective, and disposal of the spent material is easy.

Alkaline cleaners

Cleaning is an essential part of the finishing process. The cleaning method can vary depending on the contaminant to be removed, the amount of material involved, the possible need for an automated process and the overall effect on subsequent operations.

Alkaline cleaners are specifically formulated chemical blends consisting of alkaline salts, wetting agents and sequestrant (chelating) agents. They owe their detergency, or cleaning ability, to the displacement of contaminants by surface-active materials and alkaline builders. These constituents remove the contaminants and allow them to be easily rinsed away.

The term "alkaline builders" covers a broad group of chemicals: caustic soda (NaOH), caustic potash (KOH), phosphates, silicates and carbonates. These chemicals supply the alkalinity for the cleaner. High-alkalinity products saponify fats and vegetable oils into soluble soaps. These alkaline salts also neutralize acidic contaminants and aid in dispersing oils.

Caustics (KOH, NaOH), the most common type of alkalinity builders, are highly alkaline (pH 12 to 14). They saponify fats and work with surfactants to disperse contaminants. This type of builder is not safe for use on soft metals like aluminum and zinc.

Silicates provide medium alkalinity (pH 11 to 12.5) and contribute to detergency. They inhibit attack on soft metals, but they become insoluble at a pH less than 10.

Phosphates have slightly lower alkalinity values (pH 9.5 to 11.5) and provide more detergency than the other builders listed. They provide some protection for soft metals and tie up hard water ions, preventing them from interfering in the cleaning process.

Mildly alkaline carbonates (pH 9 to 9.5) are mainly used to neutralize acidic contaminants. They also buffer solutions to maintain a specific pH range.

Wetting agents (surfactants and synthetic detergents) aid in removing contaminants by lowering the surface tension of the solution, allowing the cleaner to get under the contaminant and displace it from the metal surface. Once the contaminant is in solution, the wetting agent creates an emulsion, preventing redeposition onto the part being cleaned. Surfactants have one end that is soluble in water (hydrophilic) and one end that is soluble in oil (hydrophobic). This allows the surfactant molecule to create an oil-water emulsion that is easily rinsed away. Cleaning principles. Soil is defined as matter out of place. Regardless of the type or category, all cleaners remove contaminants from a substrate by one or more of the following principles:

• solvent action - enables the cleaner to dissolve oils present on the metal surface;
• saponification - chemically converts drawing compounds (organic oils and fatty acids) into water-soluble soaps that can add to cleaning efficiency;
• detergency - surface active agents, or surfactants, reduce the interfacial tension between solution and contaminant, enabling cleaning solutions to better penetrate and displace contaminants from the metal surface;
• emulsification - surfactants in the cleaning solution suspend contaminants in the aqueous phase for easy rinsing; and
• deflocculation - disperses contaminants into very fine particles that are suspended in the cleaning solution.

Materials to be removed are classified into two general categories: oil and particulate matter. Oil, by definition, is a petroleum-based product. However, for discussion purposes, simple waxes, vegetable oils and animal fats, which may have been applied to facilitate processing operations or rust prevention, may be included. Particulate matter is finely divided contaminants present on the surface of the substrate to be cleaned, including smut, pigments, drawing materials and shop dirt.

Cleaner selection

To select a cleaner it is important to consider which metal(s) will be processed to prevent attack of the substrate. This is particularly important with aluminum, zinc and certain exotic metals.

The cleaner must be formulated to effectively remove the contaminants it will encounter. Simple, light-rust preventive oils and water-soluble coolants are easily removed with mildly alkaline cleaners at moderate temperatures. Waxes, heavy-oil rust inhibitors and other durable corrosion prevention compounds require a more aggressive product. Typically, a high-alkaline product with a good oil-solubilizing surfactant package is needed in conjunction with high temperatures.

The cleaner must also be suitable for the mechanics of the operating system. Immersion cleaners normally require different surfactant systems than spray cleaners. Also, the use of chelates is often necessary to counteract the undesirable effects of hard water salts.

Concentrate form also needs to be considered. Liquids are easy to use and can be automated. Powders are usually added manually, but they are more cost effective for most operations.

Rinsing

An important part of the cleaning process is the rinse stage. As the substrate leaves the cleaner stage it carries spent cleaner, emulsified soils and other contaminants. If not immediately rinsed, these contaminants can redeposit on the part and become difficult to remove. The rinse must remove these unwanted materials and not interfere with subsequent operations. Typically, a multi-stage rinse is used to ensure all contaminants have been removed.

Caustics and silicates, two major ingredients of cleaners, are poor rinsers. On the other hand, phosphate and phosphate blends along with blends of caustics and silicates are relatively easy to rinse. Hot water can assist in rinsing; however, care must be exercised so that drying does not occur just before the rinse tank. Double rinsing is common, using either deionized water for spot-free parts or adding a corrosion inhibitor to the final rinse if rusting is a problem.

Single stage: clean only, no rinse. This method should contain inhibition if parts are ferrous steel. It should be skimmed frequently to remove floating oils, extending cleaner life and preventing redeposition.

An immersion tank should be used for low-volume or batch work. An automated cabinet spray washer is more efficient for low-volume batch work, while a conveyorized spray is more efficient for high-volume, continuous production work. Another equipment option is ultrasonic.

Two stage: clean and rinse. With this method, frequent skimming to remove oils is needed in stage one. This extends cleaner life and prevents redeposition. The rinse should also be skimmed and changed frequently, and a rust inhibitor may be added as well.

An immersion tank, automated spray cabinet equipment with rinse cycle, conveyorized spray, auger washer or ultrasonic equipment may be used.

Three stage: clean, rinse, rinse. This system can produce the cleanest part. Stage one should be skimmed, while the stage two rinse should be kept clean by overflowing. Stage three can use deionized water for spot-free parts and/or incorporate a water-soluble rust inhibitor if needed.

Equipment options include immersion tanks, automated cabinet spray equipment with three indexed cycles (wash, rinse, and conditioned rinse), conveyorized spray, auger wash and ultrasonic.

Remember these basics about alkaline cleaning when you are researching your next cleaning system.

The Aqueous Cleaning Handbook, authored by several members of Alconox Inc., has undergone an update. Now in its 5^th edition, the handbook distills and presents practical information covering the history of aqueous detergents — what they are, how they work, and how to make best use of them.

Alconox Inc. is a New York-based firm that has been a leading global supplier of aqueous cleaners for laboratory, healthcare, industrial and related applications for over 75 years.  The handbook’s latest edition has been updated by the authors Michael J. Moussourakis, Jeff I. Phillips, Stacy R. Silverstein, and Malcolm C. McLaughlin.

“We are excited to update The Aqueous Cleaning Handbook for our customers and the wider industry,” says lead author, Michael J. Moussourakis, Vice President, Technical Marketing and Strategy at Alconox Inc.  “With the increasing demand for critical cleaning solutions in various industries, this book is a valuable resource for scientists, engineers, technicians, and everyone involved in the critical cleaning of parts and surfaces.”

Elliot M. Lebowitz, Alconox Inc. Chief Operating Officer, says, “The time and effort that our team put into this edition was inspiring. As a partner in this 76-year-old family-owned business, it makes me so proud.”

“This is a very approachable handbook with elements for those facing advanced cleaning issues for the first time as well as useful sections for the well-initiated,” adds Stuart B. Katz, CEO, Alconox Inc. and lead editor.

The Aqueous Cleaning Handbook, published by AI Technical Communications, is currently available in digital formats and can be downloaded on the Alconox Inc. website.  The digital book will also be available from selected distributors including Amazon and Barnes & Noble. 

Alconox Inc. | alconox.com

Requirements are a key driver when it comes to selecting a cleaning method.
Photo Credit: Images courtesy of SAFECHEM

What is better for metal cleaning — aqueous or solvent? The answer is: it depends. In fact, the question is rather: what are your requirements, goals and expectations? Both can be effective cleaning methods, depending on the specific context. In order to choose the right cleaning solution, you need to first understand how these two approaches differ in their working.

In aqueous cleaning, water-based detergents emulsify and encapsulate contaminants so they can be washed away. Detergents, surfactants, emulsifiers or buffers are added to the water to facilitate and enhance its cleaning performance for the removal of contaminants. The process can also be aided by heat, agitation and time. Multiple wash stations are followed by rinsing baths to remove any residues. Parts are then dried with heaters or blowers.

Solvents, on the other hand, enable the chemical dissolution of oils and greases in the cleaning solution. Metal parts are immersed in a solvent (or sprayed) that is continuously conditioned through filtration and distillation. Cleaning power can be further improved by mechanics. The parts then undergo vapor cleaning where pure solvent vapor reaches the entire surface including tiny holes, condenses on the cooler parts, thereby removing virtually any residual oil film. The cleaned parts are then removed dry following a (vacuum) drying process.

Environmental responsibility

Whether it is aqueous or solvent cleaning, both cleaning processes require diligence from users in ensuring worker safety, environmental protection and regulatory compliance.

Although water tends to be associated with sustainability or “green,” it is a finite resource. Certain water-based cleaners are also classified as more dangerous than specific solvent cleaners in their toxicological profile. Proper treatment of wastewater is therefore of crucial importance. Even if the water-based cleaners are biodegradable, given that soils generally are not, the wastewater still needs to be treated and disposed of properly.

Since solvents can give off volatile organic compounds (VOCs), the use of modern closed cleaning machines with a built-in distillation unit can significantly reduce air emissions and waste to an absolute minimum (solvent consumption is optimized simultaneously since less solvent is lost to the air and less waste is generated). State-of-the-art vapor degreasers under closed vacuum conditions are engineered to avoid any interface between operator and solvent. The vacuum operation model in closed machines also ensures that flammable solvents are safely handled.

5 key questions to consider in choosing the right cleaning solution

Choosing the right cleaning solution goes beyond meeting the required technical cleanliness. You want to do the job in the most economically viable and safest way while preserving the environment. Making the right decision, therefore, depends on several factors — technical, economic, environmental, health and safety. Some key questions you should consider include:  

1. What are your cleaning quality requirements?

Different industrial applications necessitate varying degrees of surface energy of the metal surface, which is influenced by filmy contaminations. With nitriding, for example, a higher surface energy is required than with standard coating or assembling. The required surface energy should therefore match the ability of the cleaning agent.

In aqueous cleaning, as soils and contaminations are emulsified and flooded off the surface which remain in the water (unless specific procedures are performed to purify the water), the quality of cleaning will mainly depend on the quality of the rinsing baths, as well as the number of the rinsing baths with demineralized water. The higher the required quality of cleaning, the investment and space requirements for the aqueous systems will increase accordingly.

2. What is the affinity of the cleaning agent to the soils?

Effective cleaning is based on the principle “Equal dissolves equal.” For water-based types of contaminations such as coolant and lubricant emulsions, aqueous cleaning agents are typically the first choice.

When removing mineral oil-based, non-polar contaminations, such as machining oils, greases and waxes, solvent will commonly be the preferred cleaning agent.

Above contaminations can be classified as filmy contaminations, which can be dissolved in a suitable cleaning agent. Another important category of contaminations are particles like chips, dust and residues of polishing pastes. These contaminations cannot be dissolved in a cleaning agent. To remove those, sufficient mechanics are required in the cleaning machine to flush off the particle contaminations.

The graphic shows what types of contaminations are best cleaned off by which cleaning agent. To achieve optimal cleaning results, the cleaning agent should be chemically similar to the contaminant.

3. What metal types are you cleaning and how are they configured?

In water-based processes, cleaning agents which can be acidic, neutral or alkaline, are usually matched to specific metal types. Simultaneous cleaning of different metals can therefore be problematic and this can result in compatibility issues and in worst case: corrosion. Solvents in comparison have universal compatibility with metals.

If the component parts are tiny or have complex geometry or small crevices, solvent is often recommended due to its lower surface tension and viscosity which makes it easy to wet into and evaporate out of tight spaces.

4. What is the energy demand in the process?

In water-based cleaning, significant energy is required for pre-treating and heating up cleaning water, operating high-pressure pumps, drying parts as well as treating wastewater.

Solvent vapor degreasing also requires energy to keep the entire operation under vacuum condition. Given that operating temperatures are reduced accordingly in a vacuum, the boiling point of solvent is also reduced, making evaporation quick and effective.

Vapor degreasing systems usually work vertically, compared to aqueous cleaning which often operates horizontally (a typical aqueous batch system may have one wash tank and 2-5 rinse tanks, with the number of rinse tanks depending upon the required cleaning quality). Water-based cleaning, therefore, tends to require more electricity to run.

5. What is the potential for re-use and recycling the cleaning media?  

Since dirts and soils are emulsified and rinsed off in aqueous cleaning, aqueous baths that are not treated have to be replaced frequently. Solvent can be recycled again and again via the distillation unit, which is built within the vapor degreasing system or as a separate additional system.

If there is a large amount of oils to be cleaned off, the opportunity to separate solvent from oils (via distillation) can be a particular advantage, since solvent can be effectively recovered, leaving only very little solvent residues in the waste.

The questions listed above are by no means exhaustive, and there are many more aspects to consider. Given that every industrial process is unique within its own specific context, so are the goals and the requirements. The selection of the right cleaning solution demands objective and considered evaluation. Above all else, compatibility and efficiency testing, as well as in-depth consultation with chemicals suppliers and machine manufacturers, will be crucial in helping you reach the right conclusion for your application.

For energy-efficient and fast cleaning processes, Ecoclean’s plants have effective heat recovery and can be equipped with different process technologies. Photo credit: All images courtesy of Ecoclean

Component cleaning is an essential manufacturing step in all industrial sectors to ensure requirement-compliant downstream processes and high, stable product quality. Regardless of the industry, new and modified products, increasingly compact and complex geometries, an ever-greater variety of materials, and workpiece dimensions ranging from one millimeter or less to several meters all contribute to the fact that the spectrum of required cleaning applications is more diverse today than ever before. The demands on the process and the cleanliness to be achieved vary depending on the production stage as well as on the product and industry.

For example, in the final cleaning of high-tech components, including those for the semiconductor industry, medical, sensor and analysis technology, and precision optics, particulate contamination in the nanometer range and nanolayers of residual film contamination must be removed.

In contrast, in general industry, for example, with its very different areas and components, the first task is often to clean off large quantities of chips and machining media. Frequently, factors such as high throughput requirements, heavy workpieces, a widely varying range of components and short delivery times also play a role. In addition, cleaning must, in any case, be economical, energy- and resource-efficient. 

Adapt cleaning solution to the task 

To optimally adapt a cleaning solution to the task at hand, other product and company-specific criteria must be considered in addition to the cleanliness specifications to be met. 

As a full-range supplier of solutions for industrial component cleaning, Ecoclean (Filderstadt, Germany) and UCM (the Group's division specializing in precision and ultra-fine cleaning), cover the entire spectrum of wet-chemical processes using water-based media, solvents and modified alcohols. This means that cleaning processes and systems, including the most suitable process and drying technologies for both batch and individual part cleaning, can be efficiently tailored to product- and company-specific requirements. Process design is carried out in the company’s own test centers, with cleanroom test centers with adapted plant and measuring technology available for tasks in medical technology and for high-purity applications. 

Special plants for water-based cleaning are covered by the modular EcoCvela with working chamber diameters up to 1,500 mm as well as several flood tanks and, if required, several working chambers. 

Modular system makes special chamber systems available more quickly 

With a broad range of standardized chamber systems for cleaning with water-based media, solvents and modified alcohols, as well as a wide variety of process technologies such as spray and high-pressure cleaning, ultrasonics, injection flood washing (IFW), vapor degreasing, Ultrasonic Plus, Pulsated Pressure Cleaning (PPC) and plasma cleaning, Ecoclean covers most cleaning tasks in general industry as well as the automotive and supplier sectors.

The modular EcoCstretch concept was developed for solvent cleaning applications that previously required special equipment with complex design and long production times. Among other things, it includes four working chamber sizes and several flood tanks. 

However, applications that required individually designed special equipment, for example, due to component dimensions, throughput requirements, cleanliness specifications or other company-specific factors, have increased significantly in recent years. To reduce the design effort required for this and shorten delivery times, the plant manufacturer has developed the innovative modular systems EcoCvela for water-based cleaning and EcoCstretch for cleaning with solvents or modified alcohol.

For the solvent systems, the modular concept includes four working chamber sizes with diameters from 750 to 1,200 mm and equipment with several flood tanks. For individual cleaning processes, the systems can be equipped with all process technologies available for solvent cleaning. With the EcoCvela, the diameters of the modular working chambers vary from 650 to 1,500 mm. In addition, the plants can be equipped with several working chambers and flood tanks. In these highly flexible plants, various process technologies and systems for efficient heat recovery also ensure short process times and energy-saving operation. For very high cleanliness requirements, both plant types can also be supplied with the corresponding high-purity equipment. 

With the multi-bath ultrasonic cleaning systems consisting of standardized modules, here a UCM PerformanceLine, cleaning solutions can be individually configured, for example, for ultra-fine cleaning and high-purity applications. 

Modular solutions also for multi-bath ultrasonic cleaning 

In the area of multi-bath ultrasonic cleaning systems, solutions consisting of standardized modules are also offered in the form of the UCMBaseLine, UCMSmartLine, UCMPerformanceLine and UCMHighLine model series.

With the modules for the process steps cleaning, rinsing, PPC, drying, loading, and unloading, as well as a flexible transport system, cleaning systems for a wide range of applications can be configured and commissioned cost-effectively and easily. This is also supported by the fact that the electrical and control technology is already integrated. For high-purity applications, the systems are designed with the appropriate equipment and for operation in or connection to a cleanroom. 

With its further diversified portfolio, Ecoclean enables companies from all industrial sectors to meet changing cleaning requirements not only in an economical and stable manner, but also in a resource-saving and future-oriented way. 

Hubbard-Hall is being honored with the Top Workplaces 2022 Award by Hearst Connecticut. The award is based solely on employee feedback gathered through a third-party survey administered by employee engagement technology partner Energage LLC. The anonymous survey measures 15 culture drivers that are critical to the success of any organization, including alignment, execution and connection. This is the seventh time the organization has received this honor.

“Earning a Top Workplaces award is a badge of honor for companies, especially because it comes authentically from their employees,” says Eric Rubino, Energage CEO. “That's something to be proud of. In today's market, leaders must ensure they’re allowing employees to have a voice and be heard.”

Hubbard-Hall’s roots go back to 1849 when Apothecary’s Hall, a neighborhood store which sold paints, fertilizers and sundries, opened its doors in Waterbury, Connecticut. Today, the company is a partner to more than 2,300 companies across many industries, including the military, medical, aerospace, automotive, hand tools and high-tech connectors. With personnel based out of Connecticut, South Carolina and Massachusets, the organization is poised to help manufacturers in the areas of cleaning (aqueous or solvent), metal finishing and wastewater treatment.

“The success and longevity of our company starts and ends with our people.  For anyone who works at Hubbard-Hall, we want the experience to be more than just a job,” says Molly Kellogg, Hubbard-Hall CEO and chairman. “It should challenge them to be curious, to have candid conversations and to have the courage to make decisions that move us forward.”

Photo Credit: Getty Images

Industry cleaning experts have created an online Product Quality Cleaning Workshops (PQCW) On-Demand Aqueous Cleaning Program. Barbara and Ed Kanegsberg, from BFK solutions, and Darren Williams, Ph.D., leader of the Cleaning Research Group and professor of physical chemistry at Sam Houston State University, have combined their extensive parts cleaning knowledge to create the PQCW On-Demand Aqueous Cleaning Program.

The program is a four-part, on-demand tutorial/demonstration program, which is divided into one-hour segments. Participants who pass the quizzes earn a certificate of successful completion, as well as 4 hours of continuing education credit from Sam Houston State University.

Participants can also take advantage of a bonus 30-minute discussion/consultation with a PQCW instructor with the option to group the teleconference with your colleagues (for example, four colleagues can discuss issues for a total of two hours).
 
This course helps participants learn critical cleaning from unbiased, dispassionate experts — not sales pitches. The information attained can help manufacturers improve the current process to achieve rugged, reliable aqueous cleaning; and find the best substitutes for solvent cleaning. The program also helps employees understand and minimize negative impacts of cleaning process changes by suppliers.
 
Parts of the program will be familiar. Basic principles apply to most critical product cleaning. The team has added material essential to achieve success with aqueous cleaning. Learn what is unique (and sometimes annoying) about aqueous cleaning; aqueous cleaning and the supply chain information; and how to make the most of aqueous cleaning – even if a solvent process seems simpler. The program also includes choices in cleaning forces with an enhanced tutorial on ultrasonics; and details on fixturing for successful aqueous cleaning.

The program includes a special discount offer for past workshop participants as well as a group rate savings when registering one or more colleagues. For more information, visit SHSU Online — PQCW On-Demand Aqueous Cleaning Program.

International Thermal Systems’ new location is at 3000 North 114th, Wauwatosa, Wisc. 53222. Photo Credit: International Thermal Systems.

International Thermal Systems (ITS) has moved into a new, larger facility that is eight miles from its previous location.

ITS says the new facility will provide the company with additional, upgraded space for developing precise heat processing and aqueous washing solutions for a broad array of industries, including automotive, aerospace, power generation, battery manufacturing, building products, foundry and metal packaging.

“This new, modern location is a key part of our plan to keep growing and improving our business,” says Tom Stricker, ITS’ president. “In this new location, we will continue to provide our customers exactly the solutions they expect and rely upon us to deliver. We are very excited to highlight all of our capabilities in this new space and to continue to bring fresh, new talent into our organization.”

Kolene Corporation, a leader of custom-designed and engineered molten salt bath equipment and specialty chemical formulations, has acquired Upton Industries.

Founded in 1937, Upton Industries designs and manufactures thermal processing systems in the metal heat treating industry. Upton says its Engineered Thermal Solutions methodology has enabled it to become a leader in traditional lines of heat treat equipment including box type, car bottom, lift-off and specialty furnaces using either electric heating or gas-fired systems. Kolene will maintain both the Detroit headquarters location and the Roseville location, which will be home to all Kolene’s manufacturing and fabrication. By bringing the two companies together, Kolene will reportedly house nearly 50,000 square feet of manufacturing, fabrication and commercial processing capabilities.

W. Scott Schilling, Kolene’s president says, “After thoroughly evaluating Upton’s capabilities, it was apparent that there are tremendous synergies between the two companies. Capitalizing on these synergies will allow Kolene to expand into applications and revenue segments where we have not historically been. Kolene will also have the ability to become more vertically integrated due to Upton’s manufacturing and fabrications capabilities, which will allow us to strengthen our overall margins.”

“When the opportunity presented itself to begin discussions with Upton, the similarities between the two companies and what we provide to the customers in the industries that we serve made this marriage ideal,” says Roger L. Shoemaker, chairman & CEO of Kolene.

In its 82nd year, Detroit-based Kolene Corporation provides custom-designed and engineered equipment, specialized chemical formulations and processes for cleaning and conditioning metal surfaces. Kolene reports its products are used worldwide for casting cleaning, alloy descaling, coatings removal, engine rebuild and other automotive, industrial and military applications.

The Renegade I-Series 4824 Pass-Through Multi-Stage Wash System from Renegade Parts Washers is custom designed to deliver multistage, continuous cleaning efficiency to clean and dry heavy multiported parts transported via inline conveyorized operation. Each wash and rinse stage compartment contains a 512k btu gas-immersion heater and spray manifolds with strategically placed nozzles to deliver high-pressure force and high-temperature cleaning. The 225k btu gas-heated dry stage contains dual zones with a 15-hp air blower in zone one to remove residual water — even in hard-to-reach cavities — and two 2-hp heated recirculating blowers in zone 2.

Conveyor “tunnel” or “flow-through” cleaning systems are designed for high-production, repetitive cleaning operations, and stages can be configured in any order to accommodate any production layout, the company says.

Key components of the Renegade I-Series 4824 highlighted by the company include a 48" wide × 24" height wash zone with 750-lb conveyor belt weight capacity, a gas-immersion heat system, sump sweep with dual-filtration wash cycle, power vent for rapid steam removal and a 10" PLC/HMI touchscreen with user-friendly controls and a 7-day timer. In addition, the product also comes with filter monitoring, preset maintenance, and wash cycles and temperature display. There are also other features included on the product, such as the Smart Liquid Level Sensing System with autofill functions, the Electronic Foam Sensing System, Heavy-Duty Variable Speed Conveyor Transport Systems and Rugged Stainless Steel Construction.

Industrial applications for the Renegade I-Series 4824 include aviation and aircraft, contract machining, engine, fabrication, machine tool builders, metal casting and forming, pattern and machining, precision part manufacturing, remanufacturing, transmission and transportation product centers, including mass transit.

Renegade aqueous parts washers are designed to work with Renegade detergents for maximum cleaning without residue buildup or bio-slime.

Electrocleaning pretreats parts for both rack and bulk processing. It removes soils from everything—from thumbtacks to coil-processed, 48-inch reels of steel. Today’s technology allows us to employ self-regulating, precise voltage and amperage, in conjunction with alkaline solutions. Electrical energy may be applied as direct current (DC), reverse current (RC), periodic reverse (PR) or with interruptions (IR).

Why Clean?

The usual reason for cleaning is to prepare a part for subsequent finishing—electroplating, electroless plating, painting, electrocoating, anodizing, electropolishing, conversion coating and sealing, as examples.

Cleaning should enhance the surface of the part to be cleaned. If not used properly, however, it can impair the surface. You may remove a soil and, in the process of doing this, oxidize or make the surface partially or completely inert. In this sense, you have soiled the surface with a new contaminant! But applied correctly, cleaning can enhance the acceptance of the subsequently applied coating.

A third reason for cleaning is to remove stains, oxide films, etc. Sometimes the process simply enhances cosmetic appeal. Cleaning also can facilitate handling, quality checking, visual acceptance, proper fixturing, etc.

Degreasing is another primary reason for use of any cleaning operation. But for any further surface finishing to be done properly, removal of the film left by degreasing is required. At the same time, you should recognize that, while degreasing is an excellent in-process step and while you may get proper surface preparation in the alkaline cleaner station, it is likely that another step will be required to complete pretreatment for electroplating. The limitations on use of chlorinated solvents for degreasing have increased the value and potential of electrocleaning.

Basis Metals That Can Be Cleaned

It makes life a little easier if we have some general rules of thumb as to what can and cannot be cleaned with various types of alkaline cleaners.

Any alkaline cleaner. Standard alkaline cleaners can be used on steels, stainless steels, tool steels, alloy steels, copper, nickel, nickel alloys, titanium, zirconium and lead/tin without causing a “cure worse than the disease” situation.

Inhibited alkaline cleaners. These solutions contain chemicals that prevent unwanted reactions with metals or alloys in the presence of the caustic -(OH) radical. Such chemistry is required for cleaning brass, bronze, zinc and its alloys, aluminum and its alloys, and tin—the metal itself or as plated.

Acid. There are many acid cleaners that work well in cleaning such metals as magnesium.

Cleaning processes must be tailored to handle the type of soils expected on a given part. Table I lists many soils that finishers must remove. By no means is this a complete list. But suppliers of cleaning chemicals must know what soils you are trying to remove.

Soils are generally classified as either organic or inorganic. Organic soils include oils and waxes, and redeposited soils. Inorganic soils may range from heat-treat scale, oxide films and pickling smut to polishing compounds and abrasives to shop dust.

What’s in a Cleaner?

Alkaline cleaners commonly contain carbonates, borax, sodium metasilicates, phosphates, synthetic detergents and surfactants. These chemicals have specific functions, as noted in Table II. Carbonates are added for pH control and buffering. Sodium metasilicate, as a dispersant. Phosphates, for water softening and sequestering. Borax, for buffering and dispersing. Synthetic detergents (“mini soil magnets”), for wetting, emulsifying, complexing, chelating and as biocides. Surfactants come with positive charges (cationic), negative charges (anionic) and no charges (non-ionic).

How Clean is Clean?

The definition of “clean” can be broad and flexible or as specific as your needs. The recognition of whether cleaning is an in-process step for preliminary removal of bulk soil or is a final step before a subsequent finishing operation will dictate selection of testing methods for cleanliness. Each test method has different uses in evaluating cleanliness.

Water breaks. If the surface is completely wetted when water rinsed, it is said to be free of water breaks. This is one measure of cleanliness. Many cleaners have low surface tension, however, and thus small areas of soil can be bridged over. A mild acid dip will neutralize the cleaner, and then a water rinse gives a truer picture.

Wipe. Using a fresh, clean, towel to wipe surfaces will show soils and smut remaining on the surface to be finished.

Part production. Producing parts that are uniform in appearance and/or have an adherent finish is another measure of cleaning effectiveness. But note that this is not always an indication of a properly precleaned part. Sterile operating-room implements, for example, might not take a coating uniformly because they are covered with dead germs. By definition, the germs are a soil.

Immersion copper. The ability of a copper sulfate solution to immersion deposit a uniform copper deposit on steel is an excellent “back-up” test, if there are any doubts.

Reflectivity. Reflectivity of a clean surface versus a “filmed” surface is an excellent tool in the hands of an experienced person.

Electricity for Electrocleaning

The essential parts of an electrical system for electrocleaning are 1) a source of low- voltage direct current, such as a rectifier; 2) conductors, such as cables or bus bars, to carry the current from the source to the racks of parts; 3) rheostats to control the voltage and amperage; 4) a volt meter to measure the potential; and 5) an ammeter to measure the current.

Electrical energy usually travels through utility transmission lines as 60-cycle alternating current at relatively high voltage—3,300 V or higher. But before electrical energy is used, a step-down transformer reduces the potential to 110 V for household use, or to 220 or 440 V for industrial.

To obtain the direct current (DC) needed for electrocleaning, you must “rectify” the alternating current (AC) to direct current and “transform” it from 220 or other voltage to 6–24 V. The most commonly used devices for this purpose are rectifiers.

Rectifiers. Today’s basic rectifier has five sections: 1) an AC power transformer; 2) an AC to DC rectification system; 3) power regulators; 4) controls; and 5) cooling. Overly simplified, the rectifier and transformers convert high-voltage AC to low-voltage DC. This is done using “semiconductors” that allow passage of current in one direction but not in the other.

If an alternating current comes to a semiconductor, only that half of the current that flows in the proper direction will pass through the boundary. The result is a current that is not continuous but pulsating . This is known as half-wave rectification.

If both sides of single-phase AC are rectified so as to pass in the same direction, the resulting curve represents full-wave single-phase rectification.

Typical rectification curves: half-wave rectification; full-wave, single-phase rectification; full-wave, three-phase rectification.

It is preferable and customary to rectify three-phase AC with full-wave rectification. This yields a curve that is full-wave, three-phase rectification. There is a ripple (variation) of less than 5 percent in voltage, occurring at a frequency of 360 cycles per second. This electrical current is entirely satisfactory for electrocleaning.

Tank design and anode/cathode placement are just as important in electrocleaning as in electroplating. If you can’t dislodge the soil in certain locations as positioned on a rack you are probably facing similar problems in depositing adequate electroplate thickness in these areas.

Current conductors. Copper is nearly as good a conductor as silver, and it is extensively used for conducting electricity. Aluminum has approximately 60 percent of copper’s conductivity and can be substituted. For short runs (up to 20 feet), not more than 1,000 A should be carried for each square inch of cross section of copper. For longer distances, the rule of thumb is not more than 750 A for each square inch. For example, a copper bar 2 × 1/4 inch has a cross section of 1/2 square inch and will carry 500 A for short distances and 375 A for longer distances. A round copper bar 1 inch in diameter has a cross section of 0.7854 square inch, and it could carry 800 A or 600 A for longer distances.

Aluminum has a resistivity 1.64 times that of copper. Therefore it is necessary to use a correspondingly larger cross section to carry a given current. For example, a cross section of 1.64 square inch of aluminum should be used to carry 1,000 A. When using aluminum bus bars, consider protecting the aluminum from the corrosive attack of alkaline cleaning solutions and fumes, particularly in areas near the cleaning tank.

When joining runs of bus bar, good, tight, clean connections are vital, regardless of whether the bars are copper or aluminum. Resistance caused by poor or dirty connections or contacts retards the flow of current and causes overheating. As heat is generated, resistance builds up proportionately, requiring more voltage to push current through, which in turn causes still more heat, thus multiplying the resistance.

Bus bars may be sized on the basis of temperature rise, voltage drop or energy loss. In electroplating, the usual basis is voltage drop.  You can use insulated, flexible copper cable instead of rigid copper bus. The cable is available in a number of sizes, and sometimes in two colors—black for the negative (cathode) conductor and red for the positive (anode) conductor. The insulation may be polyvinyl chloride that passes aging requirements and has the ability to function at temperatures as high as 194°F. This PVC also offers excellent resistance to acids and alkalies. A 1-inch-diameter cable does not have a solid cross section, thus the size of the cross section is not a good guide. Instead, actual current-carrying capacity may be based on temperature rise. Temperature rise is affected by whether the cable is sleeved or bare, run in open air or placed in a conduit, and if in a conduit, the number of cables in that conduit.

Some General Rules

The voltage required for electrocleaning depends on the solution formulation, current density required, temperature, anode area and the anode-to-cathode distance. If the solution concentration is too low and you are using the recommended voltage, you can generate so much oxygen in the high-current-density areas that rusting of the part surface will result. Some general rules:

• 0–6 V rectifiers are satisfactory for applications requiring 30 asf, but 9-V rectifiers are preferred.
• 0–9 V units are necessary for applications requiring more than 30 asf.
• 0–18 V rectifiers may be necessary when the racking area is extremely large or if the anode-to-cathode spacing is wide. For all bulk (barrel and basket) work, this higher voltage level is required.

Tank design for electrocleaning racked parts.

A general guide for the anode-to-cathode distance is one volt for each inch of distance. Rule of thumb: a 1- × 4-inch, 1/4-inch-thick copper bus will carry 1,000 A. Another rule of thumb—above 1,000 A, you will be generating heat, not conductivity.

To carry the current from the rectifier to the tank, the copper bus bars and anode and cathode hooks should be designed to carry amperage that will produce slightly more than the highest current density expected. Use tight, clean connections (brazed or soldered joints, or Bellville washers with bolted connections) to reduce the resistance to current flow and the resultant overheating.

Salts (from fumes) can and will accumulate at the bus bar/hook interface. These salts can actually build to the point of breaking the electrical circuit. Set up a maintenance schedule to clean contacts regularly.

Preparing Parts for Electroplating

The function of the electrocleaner is to prepare the part for steps to come. Table III provides general electrocleaning current density and time guidelines for a variety of metals. (The more exotic alloys being used by automotive, aircraft and space manufacturing should include input from a metallurgist.) Table IV presents an “ideal” preplate electrocleaning process.

Cleaning includes activating the part’s surface, which is usually done by using reverse-current electrocleaning (the work is made anodic). The terms “anodic” and “reverse” clean are often used interchangeably.

For anodic cleaning, the parts being cleaned are connected to the rectifier’s positive lead while in an alkaline electrocleaner solution. Low voltage (3–12 V) is the norm. Current densities vary from 10 to 15 asf, depending on the metal being cleaned and cleaning time allowed. Cleaning times of 1/2 to 2 minutes generally suffice for most applications. Higher current densities may be used when cleaning times are shorter. At the interface of the anodic part’s surface and the solution, oxygen is liberated. The scrubbing of these gas bubbles assists in soil removal.

Whenever possible, anodic electrocleaning is desirable for final cleaning, because the metal surface is actually being dissolved as well as cleaned. This action removes metallic smuts and prevents the deposition of non-adherent metallic films and particles. Hydrogen embrittlement also is avoided by using anodic cleaning.

Parts marred by heat treating, welding or other sources of oxides often may require a double-cleaning cycle, depending on the degree of oxidation. A mineral acid dip usually follows the final cleaner to neutralize the alkaline film on the metal surface.

To avoid etching and tarnishing, you should control current density, temperature and cleaner concentration, particularly when processing non-ferrous metals. In processing brass and zinc die castings, avoid prolonged reverse-current cleaning, high current densities, high temperatures and low cleaner concentrations, to prevent dezincification and over-etching. Reverse-current alkaline cleaning is not recommended for aluminum, chromium, tin, lead or any metals that are soluble in alkaline electrocleaners.

Tank design for electrocleaning parts in a plating barrel.

Cathodic or direct cleaning. Connecting the parts to a rectifier’s negative feed makes them cathodic. The same equipment, voltage and current densities specified for anodic cleaning are generally satisfactory for cathodic cleaning. Hydrogen rather than oxygen is liberated at the surface of the work. The volume of hydrogen liberated at the cathode is twice that of oxygen liberated at the anode for a given current density. Therefore, more gas scrubbing is achieved at the cathode than at the anode. For this reason, cathodic cleaning is sometimes employed as a pre-cleaner, followed by anodic cleaning. 

The work is actually being “plated” in a direct-current cleaner. Any positively charged material will be attracted to, and may be reduced and deposited on the surface of the part. Metallic films deposited are from ions in the cleaning solution. These films usually are non-adherent, but can be difficult to detect and remove. Such films can cause poor adhesion, roughness and/or staining of subsequently applied electroplated metals. Consequently, direct-current cleaners must be discarded and re-made more frequently than reverse-current cleaners.

Any work negatively affected by hydrogen embrittlement (e.g. spring steel) should not be cleaned cathodically unless adequate steps are taken after processing to relieve the hydrogen. Generally, heat treatment for one hour at 400°F immediately after processing will remove the hydrogen embrittlement effect. Parts with hardness exceeding 40 Rockwell C can be embrittled and must be baked after plating.

Chromium contamination of cleaners is sometimes unavoidable since the same rack is used in cleaning, chromium plating and other electroplating. Direct-current cleaning is more susceptible to staining from chromium-contaminated cleaners than is reverse-current cleaning.

Direct-current cleaning is generally used to clean chromium, tin, lead, brass, magnesium and aluminum, which are dissolved or etched by anodic cleaning. It is also commonly used to clean buffed nickel prior to chromium plating. Anodic cleaning would leave a passive nickel oxide film, which prevents the proper deposition of chromium.

In periodic-reverse (PR) cleaning, the work is made alternately cathodic and anodic, using a current of 6–15 V. PR cleaning in alkaline solutions containing sequestering or chelating agents removes smut, oxide and scale from ferrous metals. When PR is the final electroclean, the parts should leave this station during the reverse-current part of the cycle. Work may be cleaned on racks or in a barrel. Cleaning and scale removal are facilitated by alkaline cleaning solutions containing reducing and oxidizing agents coupled with strong metal chelators. One advantage of PR cleaning is elimination of acid on certain types of work where entrapment of acid allows bleed-out after alkaline electroplating. Oxides also may be removed without danger of etching or development of smut associated with acid pickling.

Interrupted-current (IR) cleaning. The theory behind IR cleaning is a simple one. At the interface of the soil on the part and the cleaning solution, a reaction is occurring. This reaction depletes the concentration of the cleaning chemicals at the interface. By turning off the power momentarily, the reaction ceases and the cleaner concentration is replenished. When the current comes back on, the solution concentration is what it should be at the interface. A typical cycle would be 8–9 seconds with current, followed by 1–2 seconds with power off. This technique is widely used in processes such as electrochemical deburring or machining, electropolishing and electroforming. If a company is using the same power source for cleaning, rather than re-rack, the finisher might use current interruption in cleaning.

Troubleshooting

Polarity. There are easy ways to determine whether a part is cathodic or anodic in an electrocleaner. If steel or copper darkens in a reverse-current cleaner, the part is probably cathodic. Substitute a piece of copper for the work being cleaned. If it brightens instead of darkening, the polarity of the work is probably anodic.

Inert smut. If the inert smut is on the work before it enters the cleaner, work is probably being degreased. Generally, work can be cleaned better and more easily if it has not been degreased. If precleaning is necessary, soak cleaning is less costly than degreasing.

Etching, rust. Steel emerging from the electrocleaner with black edges or rust-like deposits, and die castings coming out etched both indicate that the concentration of the cleaner solution is too low and/or the voltage applied is too high. Too-high solution temperature is also a possibility.

Floating layers. Floating layers on the surface of the electrocleaner solution can be caused by salt-out of surfactants, often the result of exceeding the recommended concentration of cleaner. Or, temperature may be too high, or acid may have been introduced accidentally, lowering the alkalinity of the solution.

Current density. Reduce the number of racks in the cleaner tank to increase current density. If cleaning is satisfactory, reduce the area of the part surfaces being electrocleaned or increase the current. Often, a shorter time at a higher current density will work, whereas a longer time at a lower current density will not.

High voltage, low current. If the current is low and the voltage high, check the condition of the electrodes. Remove any soil from their surfaces. Make sure rack contacts with the bus bar are solid and not insulated by corrosion or soil. Be sure tank bus leads and other junctions are not overheating, which would indicate poor contact or use of an undersized bus. Check that electrodes on both sides of the rack are operating and that there is no other load drawing from the same power source, in effect robbing the current.

Voltage and amperage low. If both voltage and amperage are low, check the AC input to the rectifier. AC may have decreased and thus lowered the DC output. Have an electrician check the rectifier to see whether bridges are worn. If amperage and voltage are apparently normal, check the area of the workload to be sure the current density is within specifications. More area than normal may have been racked, reducing the current density below that required for adequate cleaning.

Rack contacts, bipolarity. Examine the plating rack. Is it constructed to carry adequate current? Are there adequate contacts? If there is bipolar current, change the insulators on the tank.

Foam blanket. Excessive foam can be caused by drag-in of soils that produce soaps, or chemicals that act as wetting or foaming agents. Loss of the foam blanket can be caused by extremely hard water, drag-in of acid in the second cleaner of a double cleaning line, or drag-in of a different cleaner solution that contains an incompatible wetting agent.

Energy and Solution Management

In the area of energy conservation, controlled agitation of solutions in processing cycles is a viable tool. “Eductor” agitation is reported to have increased the functional available amperage by as much as 25 percent in one case. This, in turn, allowed the benefit of an increase in production processing of parts.

The second management tool is filtration. If you clean it in the cleaning station, why carry the soils and oils into following cycle stations? As much as 80 percent of the dragout soils from the cleaner redepositing on parts no longer needs to be removed in the plating station.

Thus, without major disruption of a particular process line, many-fold return of your investment is awaiting your investigation.