Slow strain rate testing

It involves a slow (compared to conventional tensile tests) dynamic strain applied at a constant extension rate in the environment of interest.

There are known cases wherein the susceptibility to stress-corrosion cracking only became evident at strain rates as low as 10−8 or 10−9 s−1.

Nevertheless, the method is very suitable for mechanistic studies, as well as for relative ranking of susceptibility to cracking of different alloys, or the aggressiveness of environments and the effect of temperature, pH, metallurgical condition etc.

The fastest strain rate that will still promote SCC for a given environment-material system is sometimes called the "critical strain rate", some values are given in the table:[6] Electrode potential and other environmental factors such as temperature, pH and degree of aeration can greatly impact the results off this accelerated stress corrosion cracking test, as can the specimen surface finish and metallurgical condition.

The departure of the ratio below unity quantifies the increased susceptibility to cracking.