Passivation after TiNi coating of 400 series SS part

[prdave00]

I've been having a general conversation with someone in my trade. He was asking who'd I suggest to passivate a 400 series stainless steel with a TiNi coating. He wasn't sure if the coating would survive a passivation per ASTM A967. Anyone think of whether this is true (I.e. the survivorship of the coating if passivated)? I suggested he passivate the part and then coat. I can't think of any benefits to passivating the part after coating. Any thoughts?

My apologies for not providing more specifics, but we never got to that point.

 

[btrueblood]

Titanium/Nickel coating?

Or Titanium Nitride (TiN)?

Either way, I don't think either coating would benefit from a "passivation". The substrate could be passivated if removal of tramp iron was deemed necessary, but it will likely de-passivate during a hot, reducing or vacuum-atmosphere vapor deposition process, and I'd think you would want the oxide layers removed to improve adhesion of the coating. Tom Walz could probably speak to that better, ask in the metallurgy forum.

 

[EdStainless]

The oxide layer is sputtered off as the first step of coating, so passivation before is of no value.
The coating it self should not contain any iron, and will not corrode, so passivation after has no value.

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Plymouth Tube

 

[prdave00]

Thanks guys. It is a TiN coating (& not TiNi as I incorrectly typed)..

Ed, what about the surfaces that aren't coated. I'll admit I don't know much about the process, but figure it's a vapor deposition process and not a line of sight or dipping process. On a TiN coated HSS end mill, for example, I always imagined only the cutting flutes were treated and the rest not exposed. I guess I need to do my homework on the process.

I think I, along with another colleague, convinced him that passivation after is of no benefit but maybe incorrectly indicated that passivation before would be advised (at least based on your comment). Ate the untreated surfaces protected from the initial sputtering process to prep the surface?