The multiple roles of an organic corrosion inhibitor on copper investigated by a combination of electrochemistry-coupled optical in situ spectroscopies

Abstract

The interaction of the organic corrosion inhibitor 2-mercaptobenzothiazole (MBT) with copper in alkaline solution was investigated by in situ infrared (IR) and Raman spectroscopy, and in situ spectroscopic ellipsometry, coupled to cyclic voltammetry (CV). At negative potentials, MBT monolayers relax on a minute time scale through MBT reorientation, leading to MBT-copper binding via S and N-atoms. After copper dissolution becomes thermodynamically feasible, including at open circuit, formation of a multilayer CuMBT complex sets in, in which thiol dominates over thione. Multilayer films effectively inhibit oxide formation. Instead, MBT oxidatively dimerises to 2,2′-dibenzothiazole disulfide (DBTA), which remains protective.