Reading ASTM G48 pitting test results
Methods A, B and C, how test conditions differ from service, and the limits of the result.
ASTM G48 uses ferric chloride solution to evaluate pitting resistance. Method A is the most common: 6% FeCl3 for 24 hours at various temperatures. Interpreting results: - Reports give critical pitting temperature (CPT) or weight loss and corrosion rate. - The test is strongly oxidising with high chloride content, harsher than most service environments, so service life cannot be extrapolated directly. - Surface condition, including welds, oxide scale and roughness, strongly affects results. Specimens should match the delivered condition. - 304 and 316L differ clearly under Method A, and 2205 is usually significantly better than 316L. State conclusions as relative ranking and suitability judgement, not as a number of years of service.