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Small 2 Stroke Piston - Adhesion Testing of Plating

We build small two stroke engines and use an aluminum nickel plated piston. We have started experiencing adhesion issues with the plating so I have been researching standard practices for testing the adhesion. I have found SAE J207 that discusses a file test and a quench test. Both seam reasonable. But I have come across some information that references glass bead peening as a test method and this method is of interest to me. However, I am having difficulty finding specific information. Does anyone know a specific ASTM/MIL/SAE spec that addresses this? If this method is applicable to my situation I would like to spec something on my print that is an industry accepted practice.

Thanks in advance

Mike Noel
Product Design Engineer - Nashville, Arkansas, United States
March 1, 2010

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Improving the quality check will provide information, but not fix the problem.
Aluminum needs to be properly cleaned, preferably with a low etch cleaner and desmut/deoxidized as required for your particular alloy. Then it needs a good zincate/strip/zincate. Good is very difficult as there are only a few poor visual clues. An alkaline EN strike is nearly mandatory. Then one rinse and into the EN as soon as possible. It worked for me, plating large aluminum pistons that had to be partially masked.

James Watts
- Navarre, Florida
March 2, 2010

Agreed. Quality inspection does not solve any problems but it should indicate the condition of a batch of parts. The supplier is doing quality checks but it did not catch our present adhesion issue. We had the vendor in today to review his process and the parameters that affect each step. We covered all of what you mentioned. Unfortunately we do not have an inspection for adhesion called out on our print and I am researching test methods that may be appropriate to our situation. If we can reach an agreement on test methods with the supplier that indicate when adhesion is unacceptable, I can document it on the print. Thank you James.

Mike Noel
- Nashville, Arkansas, United States
March 3, 2010

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Mike,

The general industry standard for adhesion testing is ASTM B571 Standard Practice for Qualitative Adhesion Testing of Metallic Coatings. It lists the three tests you found in SAE J207 plus some others. I suggest reviewing this standard with your plating supplier to determine the appropriate tests to use.

Toby Padfield
Automotive component manufacturer - Michigan, USA
March 4, 2010