On co-adsorption on passive iron from aqueous 1,2,3-benzotriazole and sodium phenylundecanoate

Passivation of iron and low-carbon steel in borate buffer solution (pH 7.40) was studied in the presence of 1,2,3-benzotriazole (BTA) and its equimolar mixture with sodium phenylundecanoate (SPU). As was shown BTA is an ineffective stabilizer of the passive state, while SPU has a better efficiency in this function. However, the stabilizing effect of BTA can be improved by forming its adsorption layer on the electrode surface pre-modified with SPU anions at anodic potential E = 0.2 V or by its co-adsorption with SPU. The analysis of attraction between the adsorbed particles of these inhibitors enabled to suggest that their co-adsorption on oxidized iron (E = 0.2 V) yields associates of SPU and BTA anions.