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-----Poor adhesion of Electroless Ni with PTFE coating onto MIM parts
We are having difficulty with coating adhesion on the following substrate:
MIM 4620 and MIM 4650
The coating is a duplex coating, high phosphorous electroless Ni plate under a high phosphorous electroless Ni plate with PTFE. All components are bulk finished and baked at 375 degrees for 24 hours. The substrate has a very good surface roughness (around 10 Ra).
Any suggestions to increase the adhesion performance of the coating would be appreciated.
Thanks,
manufacturing process engineer - Symsonia, Kentucky, USA
2004
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If you don't tell us what you're doing now, I doubt anyone is going to play the guess game. Guillermo MarrufoMonterrey, NL, Mexico 2004 I am not familiar with your substrate, but the most common adhesion problems are under or over cleaning, under or over etching, passivation of the metal before plate tank. There is a possibility that this metal will require a strike before the EN. I assume that you have checked and determined that the failure is between substrate and the first nickel and not between the nickels.(EN passivates extremely rapidly) James Watts- Navarre, Florida 2004 |
By MIM do you mean Injection moulded metal? In that case copper plating before EN will help.
Khozem Vahaanwala
Saify Ind
Bengaluru, Karnataka, India
2004
I am not surprised that you have encountered adhesion problems in duplex coating. When you deposit duplex coatings, the sudden transition from EL Ni-P to EL Ni-P-PTFE coating is likely to cause adhesion failure.
To overcome the problem, you may try to deposit the EL Ni-P-PTFE coating with a steady gradation in the level of incorporation of the PTFE particles in the coating.
T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note: The good doctor offers a fascinating blog, "Advancement in Science" )
2004
The 400 series alloys are usually chrome stainless steels. I do not know the composition of 46 series, but assume they too are chrome containing. Therefor a woods or sulfamate nickel strike is required, after proper cleaning and pickling, for good adhesion. It is not possible to achieve a high level of adhesion without a suitable nickel strike on these alloys.
Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics"
and "Plating ABS Plastics" eBay or AbeBooks affil links])
2004
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