抄録
The main stress corrosion crackings occurring on steels are chloride corrosion cracking on 18-8 stainless steel and sulfide corrosion cracking on high tension steels. In the previous paper (Part 1), the authors reported on the method of prevention of chloride corrosion cracking by means of hot dip aluminizing. Subsequently, they made experiments on sufide corrosion cracking of high tension steels by using H2S solution.
The results obtained were as follows:
1) As the results of stress corrosion tests of the specimens, the crack sensitivity of SCM-21 steel to sulfide corrosion was most remarkable at 1, 400ppm of H2S concentration, and its apparent threshold stress was about 22.0kg/mm2. In the tests of SUS-24B steel, a large number of etching pits were found, though no rupture was seen. The formation of these pits was thoroughly prevented by aluminum coating.
2) The sulfide corrosion cracking was perfectly prevented by aluminum coating on the whole surface of the specimen. However, it was not satisfactorily prevented by partial coating of aluminum.
3) The above facts would be due to the idea that the current density between the parent metal (SCM-21) and coated aluminum in H2S solution was not large enough for preventing the steels from occurrence of cracks.
