RESUMEN
Microbiologically influenced corrosion (MIC) caused by sulfate reducing bacteria (SRB) is a serious challenge in many industries, but biofilm greatly decreases the toxicity of bactericides to cell inside. d-amino acids are potential enhancers for bactericides due to their excellent performance on biofilm inhibition. However, the mechanism of d-amino acid cooperating with bactericides for MIC inhibition is still unknown. In this study, d-tyrosineï¼D-Tyrï¼and disoctyl dimethyl ammonium chloride (DDAC) were selected as the typical d-amino acid and bactericide, respectively, to evaluate their synergetic inhibition on the corrosion caused by Desulfovibrio vulgaris. D-Tyr obviously enhanced the role of DDAC in inhibiting corrosion with high corrosion inhibition efficiency at 77.23 %. The attachment of EPS and live cells on the coupon surface decreased in the presence of D-Try, leading to more cells directly exposed to DDAC. Besides, D-Try decreased the amount of live cells on the surface and thus reduced the utilization of Fe by SRB and corrosion current. Moreover, dead cells settling to the coupon surface may form a protective lay to retard the contact between live SRB and Fe, leading to slow cathode reaction and less corrosion. Therefore, D-Tyr can reduce the coverage of biofilm, thereby reducing its protective effect on SRB and achieving better corrosion inhibition effect. This work provides a new strategy for improving bactericides and inhibiting MIC.
RESUMEN
Currently, poly(aspartic acid) (PASP) is used with traditional toxic agents for corrosion inhibition, which greatly reduces the environmental significance of PASP as a green inhibitor. Amino acids, small-molecule compounds with amino and carboxyl groups, may react with PASP and act as chains to link PASP molecules, which might enhance the inhibition of PASP on metal corrosion. In this study, we selected glutamic acid (GLU) as a typical amino acid to explore the potential synergistic effect of the amino acid and PASP on corrosion inhibition via electrochemical experiments and molecular dynamics simulation. The corrosion inhibition of PASP was promoted by GLU with less weight loss and less pitting. The results of molecular dynamics simulation showed that GLU could bind with PASP at carboxyl groups and amino groups via donor-acceptor interactions and accelerate the diffusion of PASP to the carbon steel surface. Furthermore, the binding between PASP and the carbon steel surface can be enhanced by GLU, resulting in a dense and stable protective film. To the best of our knowledge, this is the first investigation into the mechanism of an amino acid as an enhancer to improve corrosion inhibition. This work provides a new strategy to enhance existing green inhibitors, which would significantly reduce the cost of cooling water treatment and its adverse environmental impacts.
RESUMEN
Microbiologically influenced corrosion (MIC) caused by biofilm is a serious problem in many industries. D-amino acids could be a potential strategy to enhance traditional corrosion inhibitors due to their roles in biofilm reduction. However, the synergistic mechanism of D-amino acids and inhibitors remains unknown. In this study, D-Phenylalanine (D-Phe) and 1-hydroxyethane-1,1-diphosphonic acid (HEDP) were selected as the typical D-amino acid and corrosion inhibitor to evaluate their effect on the corrosion caused by Desulfovibrio vulgaris. The combination of HEDP and D-Phe obviously slowed down the corrosion process by 32.25%, decreased the corrosion pit depth and retarded cathodic reaction. SEM and CLSM analysis indicated that D-Phe reduced the content of extracellular protein and thus inhibited the biofilm formation. The molecular mechanism of D-Phe and HEDP on corrosion inhibition was further explored via transcriptome. The combination of HEDP and D-Phe down-regulated the gene expression of peptidoglycan, flagellum, electron transfer, ferredoxin and quorum sensing (QS) molecules, leading to less peptidoglycan synthesis, weaker electron transfer and stronger QS factor inhibition. This work provides a new strategy for improving traditional corrosion inhibitors, retarding MIC and mitigating subsequent water eutrophication.