Multifactor ANOVA Evaluation of AZ91C Magnesium Alloy Corrosion Under Combined pH–Temperature Variations: Enhanced Protection via Stannite–Thiourea Coating–Inhibitor System

This study aims to identify and evaluate the factors affecting the corrosion of AZ91C magnesium alloy under varying pH and temperature conditions within chloride media. This study utilizes an applied methodology based on multifactor analysis of variance. Through this analysis, the factors affecting magnesium alloy corrosion can be identified, as well as the extent of their interrelationship, the relationship between these factors, and the direction of this relationship. The results indicated a combined protection efficiency of up to 76% was achieved using a stannate-thiourea (TU) system stabilized in acidic, neutral, and alkaline chloride environments. The effects of pH (6, 7, 10) and temperature (25-60°C) were systematically studied at concentrations of 3.5% and 5% NaCl for uncoated, stannite-coated, and stannite-coated samples using TU, benzotriazole (BTA), or sodium molybdate (Na₂MoO₄). Compared to the cerium phosphate-TU system in hybrid organ silane systems (82-88%) and hybrid organosilicon systems (85-89%), the stannite-TU system provides comparable performance with much simpler processing and lower cost. These results provide quantitative guidance for developing adequate corrosion protection for AZ91C alloys under varying marine, automotive, and industrial service conditions.