The surface preparation prior to applying electroless nickel over any type of substrate determines the ultimate success or failure of the plating…
Many papers have been written about the importance of proper surface preparation prior to depositing any electroplated coatings, including electro
The surface preparation prior to applying electroless nickel over any type of substrate determines the ultimate success or failure of the plating…
Many papers have been written about the importance of proper surface preparation prior to depositing any electroplated coatings, including electroless nickel. The significance and importance of surface preparation and its effect on the resulting deposit quality is too often overlooked as a primary cause of problems in the plating line. It is always easier to look at the plating tank first when trying to identify a problem. One of the significant purposes of this paper will be to identify other primary areas to focus one's efforts when problems are encountered on the plating line.
To illustrate a point, the importance of providing proper surface preparation prior to electroless nickel has many similarities to situations we encounter everyday outside of work. For example, the problems we face at home when we want to paint an item are similar to problems faced by the finisher today. The choice of color is something we can be indulgent about. Other factors, such as type of paint, are much more critical. There are many types of paints, including, epoxy, enamel and polyester to name a few. Choosing the type of paint depends on what functionality or type of service condition the part will see. An example would be the summer I painted 4 hours to earn extra money for college. I did not spend the necessary time practicing good surface preparation techniques. What I thought had been saved in time cost me many additional hours repainting that fall and into the next spring. What a valuable lesson to be learned and never lost or forgotten.
Plated coatings, especially electroless nickel coatings, are also chosen in a similar fashion. After much experience, it is soon realized and confirmed that the selection of a suitable prepaint or preplate process is as important as the selection of the finish itself.
Cleaning 101. Today as a technical service manager, I continue to see many mistakes or shortcuts taken on the plating line. If I had been rewarded with a nickel for the times I heard, "We have production to run…We don't have enough time to spend additional time in the cleaners and rinses…We don't have enough room in the line for another tank…We will let the chemistry work for us." All actions produce some consequence that will effect the resulting quality of finished parts. Unfortunately, many of the negative consequences are only realized when preparation cycle shortcuts have been taken. It is important that the proper pretreatment guidelines or best practices are followed to insure success. There are also many basics or theorems that reflect or impact the final quality of plating. The following theorems contained in the Mini-Metallurgy Course 101 provide a good basis for review.1
Mini Metallurgy Course 101
These theorems are often misused, misunderstood, disagreed with or overlooked and ignored in the haste of the production quota. The plating solution is often the primary focus when defects are found on the finished work. Our inability to realize the significance of the Mini-Metallurgy Course101 causes us to expend our energies unnecessarily. I have made many unnecessary service calls to reinforce the statement, "It has been proven many times over that 90-95% of plating problems are cleaning or preparation related." This statement is often referenced and can be found in many written articles on the subject of plating. The theorems appear straight forward, but there are many times when they are forgotten or ignored. For example, attempting to process steel, copper and brass on the same line sharing the same preparation steps will normally cause higher than acceptable rejects and be the root cause for many other problems due to substrate cross contamination.
There are a lot of good examples of proper process cycles, but there is always the need for some trial and error testing when selecting the optimal process cycle. If we could assume that any one type of part is always the same, such as having the same heat treatment scale, amount of lubricant or consistent surface finish, then the cleaning and plating process would be more predictable. Although the chemistry we use is based on science, we still require a lot of fine tuning in selecting the proper pretreatment for a particular substrate.
ASTM specifications can be a good source of information for finishing operations. These specifications are an important source of information regarding strategies for preparation cycles. The following table of ASTM B08 specification documents covering "Recommended Practices for Preparing Metals for Plating" is a good reference on surface preparation.2
Cleaning Various Metals
Nickel and Allo
ys Stainless Steels
Significance of acronyms and plating. I am a graduate from the John (Jack) Horner school of plating. I have taken the liberty to oversimplify and restate his Mini-Metallurgy Course 101 approach to surface preparation. For those unfamiliar, Jack is recognized in the finishing industry as one who, over 30 plus years, solved many plating problems through practical, yet simple approaches. He taught me that coining phrases and spouting acronyms help to categorize and file the information we learn daily. When problem solving "a person is more likely to be successful if you look for the horses first and zebras last." Simply restated, look at the basics, the obvious, before jumping to the unusual or obscure when attempting to solve problems. Another of his phrases that impacted my approach to problem 