Duplex A923 Method C Corrosion Test on Chemically Etched Sample

[minibenny]

I'm wondering if someone that has experience with A923 Method C corrosion testing and ASTM E562 ferrite point count testing could provide some insight on how surface prep might affect test results in the following scenario.

Scenario: A weld coupon of standard duplex weld (ER2209) and base metal (S31803/S32205) is sectioned, polished and etched for the E562 ferrite point count. Subsequently, the same polished and etched specimen is subject to the ASTM A923 Method C corrosion test.
In ASTM A923 Method C, it says the surface of the specimen shall not be chemically passivated by treatments such as nitric, citric, or phosphoric acid, or pickled by treatments such as nitric hydrofluoric acid, subsequent to grinding the surface.

Question 1: If the specimen is chemically etched prior to the ASTM A923 Method C corrosion test, would this typically result in more or less corrosion of the specimen, compared to a specimen that is not etched prior to the corrosion test?

Question 2: Does chemical passivation and/or pickling treatments of the surface, using any of the chemicals that ASTM A923 says not to use prior to corrosion testing, end up causing the specimen to have more corrosion than it would have if it were not treated?

 

[EdStainless]

Q1. It should result in less corrosion
Q2. In nearly every case any pre-treatment would reduce the amount of corrosion seen in the test.

A923 C is to be done on freshly ground surfaces.
A wet 120 grit is the correct surface.
If you polish finer you can artificially lower the corrosion rates.

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P.E. Metallurgy, consulting work welcomed

 

[minibenny]

Thank you, EdStainless.