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Ted Mooney, P.E. RET
Pine Beach, NJ

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Should 15-5PH Stainless Steel Pass Water-break Test After Passivation?

Like the title says. We are a NADCAP accredited facility that passivates 15-5PH aerospace components per ASTM A967, BAC5751, AMSQQP35 [canceled], etc., and are having some issues (primer/metal failure) with bonding elastomer to these smooth, machined surfaces.

One of the questions asked during our troubleshooting brainstorm is: is there surface contamination from our chemical processing tanks? The acid and alkaline cleaner baths are tested twice/week for concentration, immersion times & temps. for each lot of parts is logged, and our final processing rinse water quality is ~150 Kohm. All parts pass water-break test for 30" after alkaline cleaning, but do NOT after passivating. Is this normal?

We are also seeing the same condition with our chromate conversion coated (Alodine 1600) parts.

Thanks in advance for any insight.

Q. Hello,

I would like the answer to this question from letter no. 44492 about passivation and Alodine not passing waterbreak following the process.

The company that I work for is having difficulty with a NADCAP audit response in regards to post bond Alodine failing the required waterbreak test.

Thanks,

Kurt

A. Probably far too late to answer the original question, but it's an interesting one since water break isn't usually a concern or requirement regarding stainless passivation.

The thing about water break is that you are assuming the surface is naturally hydrophobic or non-wetting, and therefore any displayed hydrophilic or wetting tendencies is a result of surface contamination.

However if you are performing a surface process such as passivation, chromate conversion, plating, or what have you, you do not have the same surface you began with. The original surface may have been non-wetting but that has no bearing on whether the new surface is wetting or non-wetting. Therefore I would not automatically assume that failing water break means there is surface contamination without evidence that the "normal" state of the surface in question for the exact parts being processed is to pass water break.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

October 24, 2012

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