Pitting Corrosion Resistance of Alloy 690TT for Steam Generation Heat Exchanger Tube

The pitting corrosion resistance of two kinds of alloy (690TT) which experienced special heat treatment was investigated through chemical immersion test, measurement of potentiodynamic polarization curves and observation of pitting morphology by scanning electron microscopy (SEM). Pitting corrosion resistance assessment for 690TT alloy was compared between ASTM G48 A standard method and ASTM G61 standard method. The results show that in two kinds of 690TT alloy, alloy B had better pitting corrosion resistance than alloy A. The best condition of ASTM G48 A standard method for pitting corrosion resisitance evaluation of alloy 690TT shoud be 50 ℃/3 h. ASTM G61 standard method for pitting corrosion resisitance measurements of alloy 690 TT tube showed poor stability and repeatability.