Formulation Synergism Of Amino Acid Compounds As Copper Corrosion Inhibitors

Copper-based materials nowadays have been extensively employed in various essential industries, such as electric power, chemistry and machinery etc. But copper alloys can suffer severe corrosion in aerated acid media. The use of corrosion inhibitors is convenient and inexpensive. It is an important means for the protection of copper alloys. There is an inevitable tendency of substituting high-toxic corrosion inhibitors with green inhibitors. Amino acids are non-toxic, bio-degradable and relatively low-cost. They give a prospective trend in green inhibitors researches. In this paper, synergisms were investigated among amino acids and several long chain alkyl inhibitors by weight loss method, electrochemical measurements, surface analysis techniques and quantum chemical calculation. The primary results are as follows:1. The inhibition behavior of methionine (MET) combined with cetrimonium bromide (CTAB) and cetylpyridinium bromide (CPB) for copper corrosion in 0.5 M HCl solution was investigated. It showed that combination of MET with CTAB or CPB improved the inhibition performance effectively, and produced strong synergistic inhibition effect, reaching 89.0% at 50 mM MET + 10 mM CTAB. The quantum chemical calculation results indicated that the better synergistic inhibition of CTAB/MET compared with CPB/MET is attributed to their stronger electrostatic interaction between MET and CTAB.2. Both tryptophan (TRP) and phenylalanine (PHE) were investigated and showed limited inhibitive effects for copper corrosion in 0.5 M HCl solution. Their inhibition efficiencies increased with the increase of inhibitors concentrations. Corrosion Inhibition performances significantly strengthened when undecylimidazole (UDIM) at low concentrations added into the corrosive media containing TRP or PHE, and reached 87.9% at 1 mM UDIM + 10 mM PHE. Polarization curves results revealed that the complexes of UDIM with TRP or PHE inhibited both cathodic and anodic electrochemical processes, working as mixed type inhibitors.3. A self-assembled monolayers (SAMs) of Sodium lauroyl sarcosinate (SLS) was formed on the copper surface. The SLS-SAM showed protective efficiency of 60.9% for copper in 0.5 M HCl solution at assembling condition of 10 mM and 10 h. The complex SAM of SLS and glutamic acid (GLU) greatly increased its protective effect. FT-IR results revealed the formation of a chelated-film between SLS, GLU and copper ions. This film had a better hydrophobicity and better protective effect.