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EN over 304 Stainless

Good day,
I would very much appreciate some opinions on the following post.
What benefit does a pre-blast have for the adhesion of electroless nickel onto a 304 stainless steel substrate? Is a pre-blast required for good adhesion and corrosion resistance on 304 stainless? The electroless nickel in this case is a high phosphorous type, and the strike would be a nickel sulfamate strike.

Thank you,

Dan Mitchell
Aerospace Components Manufacturer - New Haven, Connecticut
2006

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First of three simultaneous responses --

A lot of this is going to be in the opinion area from whoever answers.
Abrasive blast roughens the surface so that you have more area for attachment of the plate as well as it gives it some "tooth".
There are places for sulfamate nickel strikes, but in my book, stainless is not one, especially if you ever go into the high nickel alloys. I would use a Wood's Nickel strike with rolled depolarized anodes. Absolutely do not use SD nickel rounds. Consider taking the anodes out of the tank if it is not going to be in use for a couple of days. Store in a plastic tank of water.
I liked the adhesion that I got from using the high end of the acid and the low end of the normal nickel makeup of the tank.
I think that most aerospace platers will agree with the Woods nickel strike part. Some will not like my ratios.

James Watts
- Navarre, Florida
2006

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Second of three simultaneous responses --

If properly done, the strike would suffice (I would prefer Wood's instead of sulfamate). In case of doubt about the effectiveness or quality of the strike, such as for intricate parts or parts with areas suspicious of not receiving a proper activation, the blasting might help permitting an additional mechanical lock or adhesion of the plate in those areas. In any case, the corrosion resistance has very little to do, if at all, with any of these preparation steps, for it basically depends on the internal properties of the plate.

Guillermo Marrufo
Monterrey, NL, Mexico
2006

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Third of three simultaneous responses --

You do not need to blast. The sulfamate strike is not always active enough to guarantee adhesion. Use a Nickel chloride Strike: 2 pounds pe gallon nickel chloride and 2 quarts per gallon hydrochloric acid.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2006

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2006

A pre-blast is not required for adequate adhesion on stainless steel substrates. Proper pretreatment (soak, rinse, electroclean, rinse, acid activation, rinse, Woods strike, rinse) will provide shear bond strengths on the order of 20,000 psi.

Ron Duncan [deceased]
- LaVergne, Tennessee
It is our sad duty to note Ron's passing on Dec. 15, 2006. A brief obituary opens Episode 13 of our Podcast.