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Fog rate calculation for ASTM G85

A coworker of mine asked an interesting question regarding the fog rate calculation for ASTM G85.

Paragraph 4.3.2 states that the collection rate should be 1 to 2 mLs of collection averaged over 16 hours of continuous fogging. For Annex A3, the cycle is 30 minutes of fogging followed by 90 minutes of controlled humidity.

Hence the question: Is is 16 hours of cycle testing or 16 hours of fogging (meaning one would need to run for 64 hours to get 16 hours of fogging)?

Most people I know probably use 16 hours of testing to gauge collection rates. If I'm reading the standard correctly, they should either run for 64 hours or expect one quarter of the 1 to 2 mLs standard.

I've sent an email to ASTM asking about this but haven't heard back yet. Anybody here know the answer or someone on the committee?

Christian M. Restifo
salt spray testing - Pittsburgh, Pennsylvania, US
2004

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When operating a lab corrosion testing cabinet with cyclic conditions such as this, it is neither required nor expected to take collection rates during the test. However, prior to running this test - or any lab corrosion test - run the cabinet in continuous fogging mode only and take collection rates for a minimum of 16 hours. When it has been determined that collection rates are correct, the collection devices should be removed and the cyclic test can be started.

Harold D. Hilton
- Chicago, Illinois USA
2004