Corrosion -testing methods slow strain-rate test

The sometimes contradictory results from different workers in relation to the elements mentioned above extends to other elements . Some of these differences probably arise from variations in test methods, differences in the amounts of alloying additions made, variations in the amounts of other elements in the steel and the differing structural conditions of the latter. Moreover, the tests were mostly conducted at the free corrosion potential, and that can introduce further variability between apparently similar experiments. In an attempt to overcome some of these difficulties, slow strain-rate tests were conducted on some 45 annealed steels at various controlled potentials in three very different cracking environments since, if macroscopic... 

TMO 198-98, Slow Strain Rate Test Method for Screening Corrosion Resistant Alloys for Stress-Corrosion Cracking in Sour Oil Field Service, NACE International, Houston, TX, 1998. 

N.J. Holroyd and G.M. Seamans, Slow-Strain-Rate Stress Corrosion Testing of Aluminum Alloys, Environment-Sensitive Fracture Evaluation and Comparison of Test Methods, STP 821, S.W. Dean, E.N. Pugh, and G.M. Ugiansky, Ed., ASTM, 1984, p 202-241... 

SCC susceptibility is more readily detected using slow strain rate techniques than normal tension testing. This is because the slow straining procedure allows the corrosion effects to occur [17]. Table 8 provides information on standard test methods for evaluating SCC. 

Slow strain-rate tests, in which standard tension test specimens are subjected to a constant extension rate of 10-4 to 10-6 m/s while being exposed to a corrosive environment, provide a relatively quick method for SGG screening of metals. Such methods are described in the following standards ... 

Zirconium and its alloys are susceptible to stress corrosion cracking (SCC) in such environments as Fe - or Cu -containing chloride solution, CH3OH -H hahdes, concentrated HNO3, halogen vapors, and liquid mercury or cesium [4,5]. Common test methods, e.g., U-bend, C-ring, split ring, direct tension, double cantilever, and slow strain rate tension, have been used to determine zirconium s susceptibility to SCC. 

In general, the slow strain rate test is a conservative test and a useful method for determining whether an alloy is resistant to stress corrosion cracking in a plant solution. 

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