Wet Coated Thin Barrier Films to Prevent Hydrogen Embrittlement on SUS304 Stainless Steel

Hydrogen barrier coating is a promising technology for preventing hydrogen embrittlement in metals. In this study, characterizations of hydrogen barrier films coated on surfaces of austenitic stainless steel, SUS304 of the Japanese Industrial Standard (JIS), by wet coating processes applied electro-polishing and chemical oxidation method are carried out using cross-sectional transmission electron microscopy (TEM) analyses, and then slow strain rate tensile (SSRT) tests are performed in 1.1MPa hydrogen and nitrogen gases at room temperature. The hydrogen barrier films show 200–300nm total thickness of compositionally modulated Chromium oxide dense layer. The SSRT results reveal that both the elongation and reduction of area are decreased in hydrogen gas compared with those in nitrogen gas for the non barrier-coated specimens but no significant differences appear for the barrier-coated specimens. The fracture surface of the non barrier-coated specimen shows quasi-cleavagy cracking in hydrogen gas while that of the barrier-coated specimen shows only ductile dimple fracture in hydrogen gas, indicating that the coated films effectively prevent the hydrogen embrittlement of SUS304 stainless steel in hydrogen.