Evaluation of CPT values determined by ASTM G48 practice, report on round robin tests of the corrosion committee of the Austrian society of metallurgy

摘要

A round robin test for determination of critical pitting temperature (CPT) according to ASTM G48 produced unsatisfactory repeatability and reproducibility of results in agreement with literature. Investigations on experimental procedure, identification of pits and gravimetric evaluation of samples have been performed to identify crucial parameters for improvement of results. Several recommendations within ASTM G48 practice are proposed such as wet grinding of specimens, cold drying of specimens, additional gravimetric evaluation and optical evaluation only by skilled persons. A further suggestion is a finer ground surface of samples. In order to confer statistical reference to CPT values an evaluation of medians with 50% probability of pitting is proposed.