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Interpretation of ASTM B117 requirement

2007

My name is Steven van Raay and I work for an Aerospace Manufacturer in the Auditing department and was looking for persons with experience in corrosion resistance testing to aid me in the interpretation of a requirement therein.

Specifically, section 15.1.3 requires daily records of data obtained from each fog-collecting device and goes on to reference the volume of the collected fog, the specific gravity of the collected fog, and the pH of the collected fog.

Does this requirement mean that I need to have separate results for the pH and the specific gravity for each fog collector in the same way I have separate results for the collection rate?

I am interested in what persons with practical experience have seen or practiced.

Steven van Raay
Auditor for Aerospace Manufacturer - Torrance, Calif. United States of America

That is exactly what it means. It is simple, you empty each collector into a separate,appropriate clean container, do a SG and then a pH, and dump.

James Watts
- Navarre, Florida
2007

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2007

I spoke with an individual who is directly involved with the ASTM B117 and he respectfully told me that although this is what the document says, that this was not the intent, and that persons are currently in the process of attempting to alter the specification but that there is some resistance to this.

Since the current consensus is that this IS the requirement we will alter our chamber daily check log to include 2 pH and Specific Gravity readings.

Thank you for your help.

Steven van Raay
- Torrance, Calif., United States of America

Put me in the adamant against changing group. pH of the collected solution is never the same as in the solution storage tank. Being sneaky and devious, I can change the results of salt spray by affecting the pH depending on if it is steel based or aluminum based.

James Watts
- Navarre, Florida
2007

Im sorry, I believe after your last response that perhaps the question was misunderstood. I am not talking about talking readings from the reservoir, but from the two collectors within the chamber itself and giving independent reading of pH and specific gravity for each fog collection device.

Steven van Raay
- Torrance, Calif., United States of America
2007

We do a lot of salt spray testing per ASTM B117 and we record the volume of the collectors individually and then combine them to measure the pH and specific gravity. The volume of each individual collector isn't usually enough to measure the specific gravity.

Christa Lammers
-Sylvania, Ohio, USA
2007

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B117 clearly states to collect and measure samples from two separate sites within the chamber.

Regarding insufficient collected samples: I often have 4-10 mL samples from each collection site (not enough for a hydrometer). Is it inappropriate to pipet 1mL, weigh to the nearest milligram, and record the result as specific gravity? I know that this is not entirely accurate, but it is very close.

Terry Lycans
Aerospace Supplier - Dayton, Ohio, USA
2007

When I was employed at a non-profit Government owned testing laboratory one of my responsibilities was the salt spray testing. I combined the two samples for the specific gravity and pH tests. The purpose of the testing is making sure the chamber is balanced. Its highly unlikely that a fog is such a enclosed space would have any measurable difference in specific gravity or pH.

Ron Zeeman
Coil Coating - Brampton, ON, Canada
2007

When I was doing salt spray, I used a hand held refractometer. They are relatively cheap and good ones are very accurate. Get one that measures in salinity or in specific gravity. Calibrate it with DI Water and then with a known salinity "standard". Take care of it and do not scratch the lens, PS, it only uses a couple of drops per test.

James Watts
- Navarre, Florida
2007