Seawater corrosion testing specimen evaluation

While many laboratory tests for resistance of metals to stress corrosion cracking have been developed, only a few tests are amenable to actual in-situ testing in seawater. These primarily consist of the exposure of statically stressed type test specimens such as described in ASTM G 30, G 38, G 39, and ISO 7539-2, ISO 7539-3, and ISO 7539-5. In addition, welded specimens such as described in ASTM G 58 are excellent for evaluation of the stress corrosion resistance of weldments in simple immersion tests. Evaluation of corrosion fatigue is usually limited to laboratory testing. 

Frequent use has been made of ASTM G 48, Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys fy the Use of Ferric Chloride Solution. Specimens are immersed in ferric chloride or acidified ferric chloride and are evaluated by visual examination and mass loss. A related document. Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments is found in ASTM G 78. 

Because multiple samples will normally be exposed in a seawater test program, specimens should be labeled in a maimer whereby the sample can be easily identified during sample preparation and evaluation. ASTM G 52 recommends several methods of such specimen labeling including the use of coded drilled holes, edge notches, corrosion-resistant tags, and stamped numerals. In some cases, the use of stamped... 

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