SEDL / STP / STP728-EB / STP28060S

Improving the Corrosion Resistance of Zirconium Weldments

Frechem, BS
Corrosion chemists, Rohm and Haas Co., Spring House, Pa.

Morrison, JG
Corrosion chemists, Rohm and Haas Co., Spring House, Pa.

Webster, RT
Principal metallurgical engineer, Teledyne Wah Chang Albany, Albany, Ore.

Pages: 24    Published: Jan 1981

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Abstract

Selective corrosion of zirconium Grade 702 weldments was observed in a process stream containing sulfuric acid at temperatures up to 150°C. Studies were conducted to determine the mechanism of the corrosion and to develop procedures for improving the corrosion resistance of the weldments.

Metallographic studies indicated that the dominant metallurgical factor affecting the selective corrosion is the presence and distribution of a second phase around the alpha grains. A simple heat treatment at 760 to 788°C disperses the second phase and significantly improves the corrosion resistance of the welds. The cooling rate was found to be critical only when temperatures are significantly higher than the recommended range.