Influence of extracellular polymeric substances (EPS) from Pseudomonas NCIMB 2021 on the corrosion behaviour of 70Cu–30Ni alloy in seawater
Résumé
Copper alloys, often used in cooling circuits of industrial plants using seawater as coolant, can be affected
by biocorrosion induced by biofilm formation. Extracellular polymeric substances (EPS) produced by bacteria
play a fundamental role in the different stages of biofilm formation, maturation and maintenance.
The influence of loosely bound (LB) and tightly bound (TB) EPS, extracted from marine Pseudomonas
NCIMB 2021, on the electrochemical behaviour of 70Cu–30Ni (wt.%) alloy in static artificial seawater
(ASW) and on the chemical composition of oxide layers was studied by combined electrochemical measurements
(polarization curves, EIS) and surface analysis (XPS, ToF-SIMS). Results were compared with
those obtained in the presence of bovine serum albumin (BSA), a model protein. Compared to 70Cu–
30Ni alloy in static ASW without biomolecules, for which a thick duplex oxide layer (outer redeposited
Cu2O layer and inner oxidized nickel layer) is shown, the presence of BSA, TB EPS and LB EPS leads to
a mixed oxide layer (oxidized copper and nickel) with a lower thickness. In the biomolecules-containing
solutions, this oxide layer is covered by an adsorbed organic layer, mainly composed of proteins. A model
is proposed to analyse impedance data obtained at the corrosion potential. The fitting procedure of
impedance diagrams allows extracting the anodic charge transfer resistance, from which the corrosion
current density can be calculated. The results show a slow-down of the anodic reaction in the presence
of biomolecules (BSA, TB EPS and LB EPS), and a corrosion inhibition effect by LB EPS and to a lesser extent
by BSA. No detrimental effect is evidenced with TB EPS.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...