Effects of Mo, Cu and C on the corrosion rate and the type of corrosion of 18 Cr-8 Ni stainless steels which were deformed into a U shape have been investigated in 5
N-H
2SO
4 solutions containing NaCl up to 0.4mol/
l. The results are summarized as follows:
(1) The general corrosion, the intergranular corrosion and/or the stress corrosion cracking occur according to the contents of Mo, Cu and C in the steels and the concentration of NaCl in the solution.
(2) The intergranular corrosion is mainly observed when the steels with a larger amount of Mo are corroded in a solution containing 0.2mol/
l NaCl. The stress corrosion cracking occurs in solutions containing 0.1-0.3mol/
l NaCl if the steels contain both Cu and Mo amounting repectively to more than one percent, and in a solution containing 0.4mol/
l NaCl it occurs in the steels with lesser amounts of Cu and Mo.
(3) Cl
- ion in the solutions acts as an activator or as an inhibitor of corrosion reactions according to its concentration and the chemical compositions of steels.
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