Corrosion performance of zn-al-mg coated steel wire rod for offshore application

Abstract

The increase demand on improvement corrosion protection in steel structure for offshore industry lead to development on the hot-dip galvanizing process and the coating material alloy. It is crucial to provide long service life for all this structure to minimize cost of operation, time saving, and workload. This research project focusing on evaluating the Zn-Al-Mg alloy coated on steel wire rod. Prior to Zn-Al-Mg alloy coating, the steel wire rod was coated with pure Zn followed by Zn-Al coating for comparison purposes. This is to determine effect of the intermediate layer of coating on the performance of Zn-Al-Mg coating. Electrochemical test and salt spray test were done to evaluate corrosion performance of the steel wire after Zn-Al-Mg coating. The samples before and after corrosion test were analyzed with optical microscopy, scanning electron microscopy to obtain microstructure image and Energy Dispersive Spectrometry (EDS) for elemental analysis. It was found that iron diffusion increases with multiple galvanizing process. It was also found that Zn-Al-Mg corrosion performance is good due to the presence of Magnesium (Mg) which forms protective oxide. The result shows that the Zn-5Al wire coated with Zn-5.3Al-2Mg gives better corrosion performance compared to pure Zn coated wire which were coated with Zn-2.3Al-2Mg coating.