How electroless nickel can help you position your company for recovery
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It's no secret that the difficult business environment of the past year or so has impacted everyone in our industry. In what's been called a perfect economic storm, some shops and suppliers have faced tough decisions—including going out of business.
Yet requirements for engineering, anti-corrosion, decorative and other coatings to support applications in all types of industries remain. In the relatively small domain of the finishing industry, shop owners and operators, and many suppliers, have primarily focused on trimming non-essential costs and improving operating efficiencies while scrambling to keep the doors open.
As the global economy cycles back toward some form of "normalization," plating facilities and suppliers need to position themselves to initiate and accelerate their own economic recovery. There are many methods for stimulating recovery, but focusing on activities that grow the "top line" sales for your company can provide an immediate positive impact. Also important is balancing the "bottom line" by optimizing existing technologies.
For our company, one element of recovery involves an emphasis on research and development of new technologies that will enable finishers to grow their top line by developing new markets. Our focus has been largely on niche applications and the development of technologies to stimulate efforts to break into those niches.
Finishers can also adopt this model. While new technology can add new market exposure and opportunities for any business, sustaining long-term viability requires a balance of effort to protect the bottom line, which is supported by improvements to existing core technologies. This two-pronged approach offers opportunity to open new doors with existing or new prospective clients while also taking time to better understand any efficiency to be gained with existing technology.
Here's a look at some niche EN technology developments and how they might help finishers accelerate their own recovery and improve top line sales.
Manufacturers, finishers and consumers all recognize that bright deposits have more appeal and frequently sell better than others. A majority of people are simply wired to associate non-bright plating with lower quality. As finishers, we know that non-bright deposits often will function as well as brighter deposits but offer less market appeal, so many finishers favor some color or improved market appeal driver. New market trends favoring satin or brushed plated coating appearances in components currently demand a higher value in the market.
So what about color? Black chromium, black nickel, yellow and blue passivates are indicators there is also market appeal for adding color to components. Red, black, blue, yellow and olive drab colors have all impacted the surface finishing world for functional zinc and decorative plating.
You want to grab some attention? How about purple electroless nickel? The availability of a simple immersion, non-electrolytic coloring system can offer some added decorative appeal to the "boring" yet very functional EN deposit. No longer do deposits have to be seen simply as a stainless steel or silver color.
The primary colors achievable today include bronze-yellow, brown, red, purple and blue. Colors can be used for color coding to identify left or right parts, differentiate between your high-phos EN and medium-phosphorus deposits, gain new customers/applications or enable existing customers to see EN in a different application. More importantly, ELV- and RoHS-compliant EN deposits that are given color can continue to meet those requirements. Application of post-treatments such as lacquers can further enhance the color or extend the durability of the finish. Color gives finishers something new to talk about with their existing customer base while also developing opportunities with new customers.
Color can be a selling point for finishes, but EN deposits are known mainly for their excellent mechanical properties and corrosion resistance. Performance coatings that provide or improve strength, durability, corrosion resistance and wear resistance to further enhance substrates are in high demand. What better way to achieve this than to apply EN over what some refer to as magnesium superalloys to further improve overall performance?
With the current focus on weight reduction in automotive and other applications, magnesium is increasing in use. According to the International Magnesium Association, global magnesium production in 2008 was 719,000 tons. Magnesium is now being recognized as one of the "big three" substrates utilized after steel and aluminum as a common structural component.
Magnesium alloys offer improved strength over aluminum, which makes them applicable for use in high-volume manufacturing applications such as automotive structural frames, engine components, and wheels. Aerospace applications have benefited from use of magnesium, and its good mechanical, electrical and shielding properties, plus light weight, make magnesium valuable in cell phones, laptop computers, cameras and other electronics.
While design engineers have embraced magnesium, finishers have struggled to reliably process magnesium substrates. This has given the impression that magnesium is not a good substrate for application of finishes. For many years, EN plating of magnesium substrates relied on use of heated chromic and phosphoric acids and high concentrations of fluorides, which made the process potentially hazardous for workers and the environment.
Fortunately, new chromium-free processes for EN plating of magnesium alloy substrates are now available. Production proven, they provide high reliability and reproducible results, and make working with magnesium substrates similar in ease to plating aluminum.
One important new process is direct EN plating—application of an electroless nickel deposit directly over magnesium. New processes for direct plating offer greater reliability and simplified processing compared with previous techniques. This can provide an opportunity for platers to apply more functional and/or decorative deposits to magnesium alloy substrates, offering good growth potential for any shop looking to expand their market base.
Hard chromium deposits have been used for decades in wear applications across many industries. Unfortunately, hard chrome has been subject to increasing worker safety and environmental restrictions.
For this reason EN deposits have been substituted for hard chrome in wear and corrosion applications. Many properties of EN deposits, particularly low-phosphorus alloys, make them applicable as a hard chrome replacement in some applications. In a few documented cases, electroless Ni-P alloys have even outperformed hard chromium.
Over the years, various composite EN coating alloys such as those containing PTFE (Teflon) have also been proposed as hard chrome replacements. Today, new composite EN coatings, specifically Ni-P-boron nitride alloys, can replace hard chrome deposits in many more applications. Table 1 compares the properties of EN composite coatings with a low-phos EN and hard chromium.
Table I Properties of composite EN, low-phos EN and hard chromium deposits
(15-20 vol% BN)
(15-20 vol% PTFE)
|Deposit Stress||Compressive||Tensile||Compressive||High Tensile|
|Deposit Hardness, HK100
softens with heat treament
|Coefficient of friction,
unlubricated pin-on-disc testing
Low load (0.1 kg/cm3)
High load (0.5 kg/cm3)
|Taber Wear Index, mg loss/cycle
(1-kg load, 10,000 cycles)
Heat treated to optimize deposit
|Porosity as measured by typical hours to ferrous substrate corrosionin ASTM B 117 salt spray; 25-µm deposit thickness except where indicated||24-144
Typically, 12-15 µm EN under-layer provides 25-µm total deposit thickness with composite.
More importantly, the systems to deposit these composite alloys operate similarly to mid-phosphorus EN processes, making this technology a more viable option for many shops. One system, for example, runs at pH of 6.2 and temperature of 175°F, and has a deposition rate of 10-15 µm/hr over a solution life of 7-8 metal turnovers (MTOs). Resulting co-deposits have 6-8 wt% (15-20 vol%) boron nitride with particle size range of 2000-3000 nm. Particles are uniformly dispersed throughout the deposit.
In many wear environments, the coefficient of friction (COF) of the resulting deposit is the lowest of any composite deposits tested. Unlike EN/PTFE composites, it maintains its properties in high-heat applications and provides a compressive internal stress suited for those applications where fatigue life of the component is important.
Electroless nickel technology advances are not limited to new processes. Improvements to existing processes are enabling more efficient plating of a variety of substrate materials with reduced environmental impact and metal use.
An example is EN plating on aluminum substrates without an alkaline EN strike. Before commercialization of ELV-compliant, lead- and cadmium-free EN technologies, there were some very good arguments to utilize an alkaline EN strike when plating on aluminum. For example, when using lead-stabilized Ni-P processes to plate zincated aluminum substrates in the past, it was only possible to achieve 4 MTOs before the onset of deposit blistering. Chemistry suppliers overcame this shortcoming with the introduction of alkaline EN strike chemistries designed to deposit up to 50 µin. of nickel with minimal attack of the zincate layer.
Use of EN strike technology can provide chemical cost savings of 3-8%. Despite this, implementation of these systems has been sporadic due to highly ammoniated chemistries that require good ventilation, difficulty finding space on the line to install the process, initial equipment costs and additional solution and equipment maintenance requirements.
With today's third generation of EN formulations commercially available, an alkaline EN strike is no longer needed for aluminum plating. With the proper chemistry, platers can expect solution life of >8 MTOs with an expanded operating window—all while maintaining deposition rate and deposit appearance and properties.
Another advance to existing EN processes is development of low-nickel systems. With continued volatility of nickel metal prices, it makes sense to pay closer attention to the cost of nickel in EN chemistries. For a mid-phos chemistry containing 6 g/L Ni and operated to 8 MTOs, nickel metal accounts for about 19% of total costs. Hypophosphite accounts for about 11%, making a combined total of 30% of total bath operating cost from these two strategic raw materials alone. Reducing the amount of nickel needed equates to lower costs.
Operating a low-metal EN system with nickel concentration of 3.0-3.6 g/L can provide immediate savings of $0.06-$0.10 per mil square foot, with the resulting solution and deposit performance indistinguishable to the same chemistry operated at 6 g/L. Overall, total solids content of the made-up bath chemistry is reduced by about 40-45 g/L, which extends solution life by approximately 1 MTO. This not only increases production throughput, it reduces the number of EN tank make-ups per year.
Positive environmental impacts realized from low-metal operation can be threefold: 1) Lower nickel emissions, 2) Less nickel drag-out loss and 3) Lower waste treatment costs. Overall, it's possible to show potential total savings up to 10% or more depending upon the type of work being processed.
Finally, what is often viewed as an obstacle to overcome sometimes turns out to be an opportunity. For example, a few years ago many zinc electroplaters thought it would be difficult or impossible to produce good deposits without cyanide. Today, non-cyanide zinc technology offers many advantages over its predecessor.
Similarly, the regulatory demands of RoHS, WEEE, ELV and other directives created opportunities for EN chemistry suppliers and finishers. In a sense, EN technology was reborn with the advent of these requirements.
Look at what's happened since the commercialization of lead- and cadmium-free EN formulations in 2002. Focused R&D work continues to provide advanced formulations with further operating improvements, and a new generation of stabilizing systems has given finishers the ability to utilize un-coated, stainless steel racks for EN production.
With traditional EN technology, non-coated racks would be subject to unwanted plating. This was not only a waste of EN chemistry, it necessitated stripping of racks after each cycle or end of production day. Today, many platers use an uncoated rack to part surface area ratio of 0.3 ft2 of rack for each square foot of parts. Some finishers run even higher ratios.
Our studies have shown that third-generation ELV-compliant EN technology that does not plate racks results in significant savings for finishers. With uncoated racking systems and the wrong EN technology, 20-40% of total EN cost can be wasted on plating of racks. So, if a finisher's chemistry cost is $1.50/mil-ft2, the cost of plating uncoated racks would be $0.30-$0.60 mil-ft2. Add in the costs of stripping chemistry and the more frequent waste treatment cost of the stripping solution, and it's easy to see how these newer EN formulations are helping finishers keep more money in their pockets.