Mechanistic study on the corrosion behaviour of Zinc and Zinc-Calcium alloys designed for enhanced metallic coatings in the presence of chloride and phosphate ions

Additions of 1 wt.% Ca were made to Zn (Zn-1Ca) generate favourable chemical conditions during corrosion for enhanced performance phosphate inhibitors. Zn-1Ca displayed a reduced rate in 0.17 M NaCl measured using the Scanning Vibrating Electrode Technique and polarisation. In-situ timelapse microscopy SEM-EDS demonstrated that intermetallic CaZn13 preferentially corroded releasing Ca2+ increased product precipitation, cathodically deactivating system. × 10?3 mol dm?3 additions decreased Zn-1Ca. Inhibition was greater where uniform precipitation mixed metal phosphates produced anodic cathodic inhibition.