抄録
The effect of prestrain on intergranular corrosion was studied to infer the relationship between the preferential dissolution of grain boundary and lattice defects of sensitized Inconel 600 alloy in H2SO4-NaCl solution.
The polarization curves showed that prestraining decreased passive current densities and shifted starting potentials of trans-passivity (Etps) to less noble side. The intergranular corrosion rates at Etps +51mV decreased with increasing prestrain. Those values at 980mV decreased up to the prestrain of 10% but showed a tendency to increase with higher prestrain. This relationship between the intergranular corrosion rates and prestrain found under no stress also stood under the constant load of 90% proof stress for 0% prestrained specimen. But the intergranular corrosion rates under the applied stress of 90% proof stress for each prestrained specimen increased with increasing prestrain because of the introduction of continuous plastic deformation at intergranular corrosion tips.
EPR values increased with increasing prestrain. After measurements of polarization curves, sensitized specimens showed intergranular corrosion and 30% prestrained specimen of solution annealed condition showed localized one as well. Therefore, it is thought that the intergranular corrosion in an active region is accelerated by prestrain.
It is concluded that prestraining accelerated the intergranular corrosion in an active region but suppressed it in a trans-passive one.
