Observation of Hydrogen Distribution on Pt, Pd and Type 304 Austenitic Stainless Steel by Silver Decoration Method

Abstract

Silver decoration method was applied to platinum, palladium and type 304 austenitic stainless steel to visualize the hydrogen distribution in those metals. The electrochemically hydrogen-charged specimens were dipped into the silver decoration solution of K[Ag(CN)2]. The silver decoration process was confirmed to be caused by the reduction of the silver ion by hydrogen for all specimens because hydrogen-charged area was decorated by the metallic silver while hydrogen non-charged area was not. The silver decoration was found to be favorably performed for the specimen with higher hydrogen solubility. The decoration capability strongly depended on the pH of the decoration solution, and there was an appropriate pH condition for appearance of the clear image of hydrogen distribution. In the case of type 304 stainless steel, the different densities of silver particles from grain to grain in the substrate are observed, suggesting that the desorption rate of hydrogen is dependent on the orientation of the grains in it.