The Use of Quaternary Phosphonium Compounds as Antibacterial Corrosion Inhibitors for Low-Alloy Steel

Triphenyl-based quaternary phosphonium compounds were evaluated as corrosion inhibitors with biocidal properties for controlling microbiologically influenced corrosion. Several compounds displayed biocidal activity for acid-producing bacteria or for sulfate-reducing bacteria, but not both. Electrochemical impedance spectroscopy was used to examine the effect of the compounds on the corrosion behavior of a low-alloy steel Fe-Ni-Cr-Mo (HY-80) in deaerated artificial seawater with and without bacteria present. The performance of the compounds as corrosion inhibitors appeared to be governed by steric factors. Tetraphenyl phosphonium chloride and cinnamyl triphenyl phosphonium chloride were effective as antibacterial corrosion inhibitors.