Corrosion Behavior of Zinc Alloy Layers

Résumé

The alloying of zinc with some additional elements in specific quantities could be reliably used in the hot-dip coating process. These elements conferr substantially improved performance to the end-product specially by improving corrosion resistance.
In this paper the influence of adding different percentages of aluminum and bismuth into the zinc bath was researched.
The technological conditions for obtaining zinc-bismuth-aluminium coatings with 0.27% - 0.52% bismuth and 0.11% Al are presented. The degree of microalloying and assimilation in the zinc bath was determined by spectrometric analysis of alloy samples, taken from the melt at different time intervals.
Corrosion resistance of the layers was assessed by two types of tests: corrosion behaviour in seawater for a period of five weeks and electrochemical tests in 3% NaCl solution. Both applied corrosion tests show an increase in corrosion resistance to bismuth content increasing and metallographic analysis of samples corroded shows a general corrosion process.