Depth of Atmospheric Penetration of Stainless Steel in Contact with NaCl, MgCl_2, and Seasalt under

摘要

The atmospheric corrosion behavior of stainless steels in contact with chlorides was studied in a laboratory atmosphere. Following Shoji's method, nine droplets consisting of 5 mu 1 of 0.5 N Cl~- solution each were put on a stainless steel specimen and dried. The specimens were then exposed in a humidity-controlled chamber for three to six months. Penetration depth at the deposit strongly depended on RH. The maximum penetration depth was obtained at 50 percent RH for 430 steel and 33 percent RH for 304 steel with deposits of seasalt and MgCl_2, but no penetration was observed with deposits of NaCl at 33 percent and 50 percent RH. At 75 percent RH all three kinds of salt gave no penetration for 430 and 304 steels. The test was extended to seven other steels, and penetration was summarized in terms of Pitting Resistance Equivalent = (percent Cr) + 3.3(percent Mo) + 16(percent N).