Influence of Boron Concentration on the Corrosion Resistance of High Boron White Cast Iron to Liquid Zinc Bath

The influence of boron concentration on corrosion resistance of high boron white cast iron dipped into a pure liquid zinc bath at 460°C was investigated. The results reveal that high boron white cast iron containing 3.5 wt.%B exhibits excellent corrosion resistance due to the dense continuous netlike or parallel Fe2B phase which hinders the Fe/Zn interface reaction. The corrosion rate decreases significantly when the boron concentration increases, but the corrosion rate declines slightly when the boron concentration exceeds 3.5wt.%. EDS results indicate the coarse and compact δ phase generated near the matrix and a large amount of massive and blocky  phase occurred close to the liquid zinc. The corrosion process includes Fe/Zn interface reaction and the spalling and fracture of Fe2B. The failure of Fe2B is mainly caused by the microcrack of phase transformation.