Correct Specification for stainless steel passivation

[chimps12]

Hello,

I am trying to create a standard note for passivation. We have been having parts made overseas (China) and I want to provide them with a more clear understanding of what we want.

The parts are 410 CRES heat treated to HRC 38-42.

Currently the drawing notes states "FINISH: PASSIVATE"

I am thinking of updating this with the note "CLEAN AND PASSIVATE PER ASTM A967, PASSIVATE AFTER HEAT TREAT AND HARDNESS VERIFICATION" with the requirement being the shops in China purchase and follow this spec.

Is this enough or should there be further information in the note? I.E. nitic vs citric, type, etc. Also, I see there are other specifications used for passivation. ASTM 380, AMS 2700 and the obsoleted QQ-P-35.

The parts we make are not aerospace and are used in test equipment for semiconductor chips. So I do not think I need the AMS or military spec (unless there is a good argument for AMS 2700 being better than ASTM). However, should I include both the ASTM 380 and the ASTM A967? It appears there may be some overlap with these specs, ASTM 380 specifies more about the cleaning process with a little bit about the passivation and ASTM A967 goes into further detail about passivation. I am trying to keep the drawing as clear and to the point as possible and not wanting to overload it with a bunch of specs if thay are redundent.

Thanks For Your Help,

 

[dgallup]

I would pick one spec and stick with it. Multiple specs probably have some inconsistencies or conflicting requirements. If you don't care whether they use citric or nitric acid then don't specify it. If it makes a difference then do.

How are you going to inspect the parts to verify the passivation took place? Some specs will have a clause about certification and reporting that might be useful. The problem is you have to buy all the specs before you know which one is best for you.

Good luck on getting a Chinese supplier to actually purchase the spec.

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