Effect of protein adsorption on the corrosion behavior of 70Cu–30Ni alloy in artificial seawater

• A model is proposed to analyze electrochemical impedance diagrams plotted at Ecorr.
• Without BSA, an outer Cu2O layer and an inner layer of oxidized nickel are shown.
• BSA leads to a mixed oxide layer composed of CuO, Cu2O, and Ni(OH)2.
• The BSA has a slight corrosion inhibition effect at the corrosion potential.
• BSA induces lower amount of redeposited Cu2O and lower oxide layer thickness.

Copper alloys often used in cooling circuits of industrial plants can be affected by biocorrosion induced by biofilm formation. The objective of this work was to study the influence of protein adsorption, which is the first step in biofilm formation, on the electrochemical behavior of 70Cu–30Ni (wt.%) alloy in static artificial seawater and on the chemical composition of oxide layers. For that purpose, electrochemical measurements performed after 1 h of immersion were combined to surface analyses. A model is proposed to analyze impedance data. In the presence of bovine serum albumin (BSA, model protein), the anodic charge transfer resistance deduced from EIS data at Ecorr is slightly higher, corresponding to lower corrosion current. Without BSA, two oxidized layers are shown by XPS and ToF-SIMS: an outer layer mainly composed of copper oxide (Cu2O redeposited layer) and an inner layer mainly composed of oxidized nickel, with a global thickness of ~ 30 nm. The presence of BSA leads to a mixed oxide layer (CuO, Cu2O, Ni(OH)2) with a lower thickness (~ 10 nm). Thus, the protein induces a decrease of the dissolution rate at Ecorr and hence a decrease of the amount of redeposited Cu2O and of the oxide layer thickness.