Effect of Surface Aluminizing on the Zinc Corrosion Resistance of Fe-20Cr-5B-3Al Alloy

This study systematically investigates the effect of surface aluminizing treatment on the microstructure of Fe-20Cr-5B-3Al alloy and its corrosion behavior in liquid zinc. Aluminizing treatment was performed using the powder pack method with NH₄Cl (5 wt.%) as a catalyst. Aluminide layers were prepared on the surface of the Fe-20Cr-5B-3Al alloy, and the microstructure of the aluminide layer was observed and analyzed. The corrosion performance of the alloy in liquid zinc was compared before and after aluminizing treatment in a 128 h corrosion test. The results show that after aluminizing treatment, the α-Fe phase on the alloy surface transforms into the Fe₂Al₅ phase, while the original Fe₂B phase breaks into finer structures that disperse over the Fe₂Al₅ phase. The Cr₂B phase is not affected and maintains its structural integrity. After 128 h of exposure to liquid zinc, although the alloy exhibited good corrosion resistance in liquid zinc, the α-Fe phase was still preferentially corroded, with zinc liquid infiltrating along the α-Fe phase toward the interior. In contrast, after aluminizing treatment, the transformation of α-Fe into Fe₂Al₅, which has excellent corrosion resistance, significantly reduces the corrosion rate and enhances the alloy's resistance to liquid zinc corrosion.