Hydrogen-Stress Cracking of Type 301 Stainless Steel Clamp

Several type 301 half-hard stainless steel clamps used to hold cylindrical galvanized steel covers to galvanized cast iron bases failed in flooded manholes after one to six months of service. Before service, they were treated with antiseize compound containing MoS2. Based on the conditions (the clamp is the cathode of a galvanic cell with zinc) and the brittle nature of the cracks, the failures were diagnosed as hydrogen-stress cracking. Laboratory experiments were conducted to substantiate the above diagnosis and to evaluate the effect of annealing and the hydrogen-stress cracking behavior of type 316 stainless steel. The problem was solved by changing the clamp material from type 301 to type 316 stainless steel and by eliminating the MoS2 antiseize compound.