Polystyrene films as barrier layers for corrosion protection of copper and copper alloys

• Sub-micrometre thick, dip-coated polystyrene (PS) coatings were prepared.
• PS coatings inhibited the corrosion of Cu alloys in various aqueous environments.
• The thickness was adjustable by the concentration of the PS stock solution.
• Surface free energy and surface coverage values improved with increasing thickness.
• Adhesion of Desulfovibrio alaskensis cells was substantially prevented.

Dip-coated polystyrene layers of sub-micrometre thickness (85–500 nm) have been applied on copper and copper alloys (aluminium brass, copper–nickel 70/30), as well as on stainless steel 304, and produced an effective barrier against corrosion and adhesion of corrosion-relevant microorganisms. According to the dynamic wettability measurements, the coatings exhibited high advancing (103°), receding (79°) and equilibrium (87°) contact angles, low contact angle hysteresis (6°) and surface free energy (31 mJ/m2). The corrosion rate of copper–nickel 70/30 alloy samples in 3.5% NaCl was as low as 3.2 μm/a (44% of that of the uncoated samples), and in artificial seawater was only 0.9 μm/a (29% of that of the uncoated samples). Cell adhesion was studied by fluorescence microscopy, using monoculture of Desulfovibrio alaskensis. The coatings not only decreased the corrosion rate but also markedly reduced the number of bacterial cells adhered to the coated surfaces. The PS coating on copper gave the best result, 2 × 103 cells/cm2 (1% of that of the uncoated control).