Studies On The Use Of Alkyl Esters Of Carboxybenzotriazole As Inhibitors For Copper Corrosion

摘要

A series of alkyl ester mixtures (methyl, butyl, hexyl, octyl) derived from Carboxybenzotriazole have been studied as inhibitors for copper. The inhibition efficiency (IE) is concentration, time and pH dependent. At pH ～ 0, the IE of the octyl and hexyl ester mixtures are considerably higher than that for benzotriazole under similar conditions. As pH increases up to approximately 8 the IE of these two esters is decreased, but are still sufficient for practical use. For the butyl and methyl esters, an opposite trend was observed with the change in pH. That is, IE increased with increased pH. In acidic sulphate solution (pH ～ 0) the IE was in the order: octyl > hexyl > butyl > methyl, whilst in the near-neutral solution (pH ～ 8) this order is reversed. This suggests that at low pH IE is determined by Van der Waals' forces of attraction between adjacent alkyl chains oriented away from the copper surface, which are increased with the length of the alkyl chain. It is proposed that the protonated species (CBTAH_2~+-R) are chemisorbed on the copper through an azole nitrogen. On the contrary it is proposed that at high pH a polymeric complex is formed that is less protective. Polarisation and SERS studies confirm this hypothesis.