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"384 hour salt spray FAILING-Spec. WSS-M21P17-B3"


I have submitted parts with Plating Specification WSS-M21P17-B3. The salt spray tests is for 384 hours. Thickness minimum is .00031" (inches). The parts passed minimum thickness and measured @ .00055"-- more than the minimum requirement. The salt spray however failed at around the 200-hour mark.
Is 384 hours achievable?
If it is, why did these parts fail?

Don Istvan
- Canton, Michigan


Dear Sir:

according to:
S437 WSS-M21P17-B3 :Electrolytic zinc plate, w/trivalent clear chromate, Leached and sealed, Integral torque control lubricant Trivalent 96W/384R

S437 WSS-M21P17-B3+wss-m4d240-a2(nylon):Electrolytic zinc plate, w/trivalent clear chromate, Leached and sealed, Integral torque control lubricant + type 2 nylon Trivalent

Concerning 384 hours achievable, I know lots of Taiwan mfgrs. can do it easily!
"The products failed @200SST":I think mostly arises from trivalent Cr and sealer!

Best regards,

Brian Chang
- Taiwan



The WSSM21P17 B3 specification calls out a specific finish that can only be applied by licensed applicators. These applicators are audited on a quarterly basis, and parts routinely pass both the white and red corrosion requirements, with and without thermal shock.

I suspect the finish you are evaluating is something other than what is approved by Ford Motor Company.

Please contact me for more details.

Mike Wyrostek
Macdermid - Waterbury, Connecticut, USA
supporting advertiser


I'll agree with everyone but would like to point out a couple of other issues. First to Mike: Yes a specific product is specified however, exceptions are frequently granted to products that produce a finish that passes the performance requirements of the specification. This is partially due to legal issues (I prefer not to be more specific then to say that they revolve around areas of antitrust actions and collusion) and practical respects (the use of only licensed shops would greatly reduce the pool of potential suppliers especially in some geographic areas).
From a technical standpoint, no matter what products are used, if they are not properly applied and the entire plating process not properly operated they will fail. High organics in zinc plated deposits will cause failure to red corrosion. Improper handling of parts will cause failures. Also be sure the testing protocol is being properly followed.

Gene Packman
- Great Neck, New York

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