The authoritative public forum
  for Metal Finishing since 1989
  

 

-----

Complying with A-967 with many materials

November 17, 2011

Ted and the Finishing.com cloud:

I have a client who I am helping validate his processes for HIS client. He has been passivating 17-4 PH for years without any issues. Plus the results of his passivation using the A-967 testing protocols have always passed.

Well it seems his client is asking him in the form of his blueprint references to comply with A-967 (with no other specific requirement). In reviewing his process, it may not be in strict compliance with A-967, and his Nitric solution does not agree with any of the choices in the spec. But I also see what I think is a discrepancy in the spec. Fig X1.1 of A-967 speaks to the solution types to be used for various materials. yet para 4.2 of the spec says the Seller can choose their own treatment. Since Appendix X1 is "non-mandatory", can I ignore it?

The client wants to passivate 200, 300 series austenitic stainless, machined stainless, as well as the PH and martensitic grades using the same acid bath for all materials. They have been using Nitric at 20-40% (1.11-1.21 SG) for a minimum of 20 minutes at a temperature of 120-150 °F. Nitric 5 says you can do anything so long as it passes. And they have. So are we good? Reading many of the threads in this forum wold suggest this is most of an art than a science, so anything that works should be fine. And so far, his process has been working.

Even though we might be okay, I'm also wondering if the recommendations have been written for a reason and we should use different solutions as outlined in Fig X1.1 because they have been most successful for each material type.

Any advice would be helpful.

TIA

Tom Smith
Consultant to a company doing passivation - Chatham, New Jersey, USA