Etch pitting and subsurface pore growth during the thermal etching of silver

Abstract

The thermal etching of silver was extensively studied in the middle of twentieth century, revealing the key role of oxygen on surface morphology changes including: grains striation, grain-boundary grooving and etch pitting. Here we probe the role of the subsurface and defects induced by rolling on the thermal etching of pure silver sheet. Nanometre- and micrometre-sized faceted pores have been observed in the subsurface region after heat treatments in air. The relationship between these subsurface pores and rolling defects is demonstrated. A mechanism for the formation of subsurface pores based on the precipitation/reaction of dissolved oxygen is suggested which can also explain the aligned etch pitting observed.