On the Cathodic Protection of Metals (3rd. Report). On the Cathodic Protection of 13 Cr Stainless Steel

Cathodic protection of 13 Cr stainless steel was studied. In dilute HCl and H2SO4 solutions, 13 Cr stainless steel suffers some what from cathodic corrosion, and it can be fairly protected by cathodic current. But in dilute HNO3 solution, cathodic corrosion occurs just like in 18-8 stainless steel, as described in the previous paper. The conclusions of the 2nd and the 3rd reports are as follows: (1) The cause of cathodic corrosion of 13 Cr and 18-8 stainless steels is due to reduction of the protective oxide film on their surfaces. (2) In the case when the surface film gives good corrosion resistance to the alloys, cathodic current is of no use. But in the case when free corrosion is of a certain value, cathodic protection is effective in suppressing its occurrence.