HYDROGEN EMBRITTLEMENT OF STEEL IN METAL FINISHING PROCESSES OF BLACK OXIDE AND ZINC PHOSPHATIZE

Static load tests were conducted with notched, steel tensile specimens after processing in black oxide specification MIL-C-13924 Class 1 and also after processing in zinc phosphatize solution specification MIL-P-16232C Type Z, to determine embrittlement characteristics of these processes. The scope of work was limited to a brief survey to determine whether the problem was serious for these processes. Results based on the use of types 4140, 1045 and 1095 steel specimens at hardness of Rockwell C 50 show that embrittlement is not a problem with the black oxide process. The zinc phosphatize process is critically embrittling, and relief treatment for higher strength steels is advisable.