MCC [Materials Characterization Center] corrosion tests at reference testing conditions for A27 cast steel in Hanford ground water

The corrosion of A27 cast steel in synthetic Hanford ground water was characterized by uniform wastage of the metal with no evidence of pitting or intergranular corrosion. The average corrosion rate decreased with increasing test duration which indicated that the corrosion rate for long time periods can be conservatively predicted for conditions simulated by these tests. The corrosion products for the static and flowby tests were very similar and consisted of a gel-like, very adherent, amorphous layer next to the metal with adherent packing material (basalt = bentonite) attached. The corrosion product for the air/steam tests was a very thin, asherent layer that was uniform over the specimen surfaces. No spalling was observed for periods as long as 120 days. The amount of corrosion for the air/steam tests at 3000C was very small with an average corrosion rate of 1.62 μm/y for 120-day tests. The corrosion rate decreased with time and there was no indication of localized corrosion. A comparison of interlaboratory results for the three kinds of corrosion tests indicated that a relative large component of variability occurred between laboratories compared to smaller variations within each laboratory. For the longest tests compared, the total individual specimen relative standard deviations, including within-laboratory variations and between-laboratory variations, were 12% for the 120-day pressure vessel tests, 15% for the 300-day flowby tests, and 26% for the 120-day air/steam tests