Rather than scrapping reject parts, chemical stripping may prove to be a cost cutting and competitive decision. You can even benefit from using the process on paint racks, masking pieces and parts finished with rust, corrosion or tarnish protective coatings. Read on to discover how the process of industrial metal cleaning can help you trim costs and eliminate hazardous chemicals in your workplace, among other benefits.
Chemically stripping metal parts can be an extremely beneficial process in any industry, whether it’s metals, finishing, glass, transportation, etc. After all, any type of finishing operation, including painting, plating and porcelain enameling, require that metal surfaces be free of protective oils or lubricants to obtain satisfactory adhesion. In addition, painting and plating leave residues that must be removed to prevent contamination of subsequent batches.
When you send parts to a company that specializes in chemical stripping, you automatically eliminate the need for hazardous chemicals in your workplace and avoid metal fatigue in your racks that can be caused by using burn-off ovens. Be sure to check into whether or not the company you choose has an environmentally safe process and a Part B approved TSD facility to handle waste. Other benefits to chemically stripping paint and other coatings from metal include the following:
- Eliminating the cost of remanufacturing the original part;
- Capability to strip tough configurations;
- Removing most coatings, including urethanes, epoxies and powders; and
- Efficiently stripping virtually any surface without harming the basic metal or distorting the structure.
Since this procedure leaves absolutely no residue and reveals bare metal, the part can then be returned to the plater or coater clean and ready for reprocessing.
Cleaning Basics: Cleaners, Parts and Soils
There are three general types of industrial cleaning materials:
- Solvents that may or may not be self-emulsifying;
- Alkalines that may or may not contain soaps or other surface active agents; and
- Acids that contain solid or liquid acidic materials and may or may not be compounded with surface active agents, inhibitors or special solvents.
Each type of cleaner can be applied by hand, in soak tanks with or without electric current, with a spray washing machine or steam gun.
Although metal cleaning is exceedingly complex, there are some standard factors that influence the selection of cleaning materials, including (but not limited to) the surface to be cleaned, material to be removed, degree of cleanliness required, application method, water quality, cost of complete cleaning operation, operator safety, parts being cleaned, equipment and disposal of spent solutions.
One benefit to chemical stripping is its range of application. Virtually anything, including aluminum, brass, bronze, concrete, copper, galvanizing, glass, iron, lead alloys, magnesium, Monel metal, nickel, nickel silver, painted surfaces, plastics, silver, steel, stainless steel, tin, wood and zinc, among others, can be cleaned.
Likewise, the number of soils that can be removed from surfaces is just as large and includes slushing oils, cutting oils, buffing compound residue, heat scale, rust and corrosion products, quenching oils, heat treating salts, drawing compounds, smuts, paints and inks, lime scale, “burned on” carbon deposits and tarnish films.
Factors Affecting Cost
Ideally, cleaning costs should be reported in terms of cost per thousand sq ft or cost per thousand parts or pieces. In addition to the cost of the cleaning material per lb, the cost of floor space, equipment (and its maintenance), heat, water, electric power and labor, will impact the total cost of any cleaning operation. The cost of cleaning material to charge a tank, plus the cost of daily upkeep until the solution is discarded should be divided by the number of sq ft of work, the number of pieces cleaned or the number of days or hours of actual use to determine true cost of the cleaning material for comparison purposes.
Safety Precautions: What You Need to Know
When it comes to selecting a company to strip your parts, there are some important issues to be aware of to ensure that the company you use is properly equipped and able to handle and recycle generated waste materials.
- In handling and using solvent detergents, the facility should be adequately ventilated, and flammable solvent detergents should be used at temperatures below the flash point. Open flames, sparks and grinding operations should not be allowed in areas where solvent detergents are being used.
- When it comes to making up solutions of heavily alkaline materials, the company should add the material slowly to cold water to avoid violent reactions. Subsequent additions should be predissolved in cold water before adding to a hot solution.
- Finally, be sure that tanks for holding acidic solutions are constructed of materials not attacked by the particular acid in use.
For information about regulations regarding disposal of spent solvent, alkaline and acidic cleaning solutions, consult your local Department of Public Works for exact details because regulations vary from city to city and state to state.
How Is the Surface of the Part: Protected during Chemical Stripping?
Again, one of the many benefits of chemical stripping is that the part’s surface is not harmed in any way. For instance, inhibitors incorporated in alkaline cleaning materials are specially designed for sensitive metals. These inhibitors deposit a thin protective film on the bare metal as soon as all oils or greases are removed. This film prevents the alkaline in the cleaning solution from chemically attacking the sensitive metal.
After the alkaline cleaning solution removes all soils, the part is covered with a film that adheres to its surface. If the film were allowed to remain on the surface, it would interfere with the adherence of any subsequently applied protective coating, such as paint or metal. Therefore, rinsing is considered an integral part of any cleaning operation. Just as the cleaning solution removes objectionable soil from the surface of the part, so the rinse water removes the cleaning solution, which is also an objectionable soil on the surface of any part intended for refinishing.
The process of chemical stripping is as old as painting itself. In recent years, however, the type of chemistry associated with chemical stripping has evolved a great deal. The impact of health and environmental regulations has challenged the industry to conduct more research and experimentation to find environmentally friendly alternatives. Industry leaders are more frequently turning to solvents like N-methyl pyrrolidone to efficiently and effectively strip metal without toxic side effects.
With its range of applications and its cost-cutting benefits, the process of chemical stripping is an economical choice for any company looking to trim costs and recycle its resources. Recent trends show support for an overall industrial social conscience and governmental regulations regarding the handling and disposal of hazardous chemicals. Chemical stripping industry leaders are striving to research and experiment with new alternatives to toxic chemicals for the benefit of their customers and the environment.