Novel composite sacrificial anodes based on high phosphorus blast furnace metal with minor Zn addition

Abstract

The present work discusses the development of novel composite sacrificial anodes based on blast furnace pig iron extracted from abundantly available high P (0.9 wt%) scrap with minor Zn addition (1, 2, 3, 5, and 10 wt% Zn). The incorporation of Zn beyond 1 wt% to the pig iron decreases the working potentials to much negative values below −0.811 V vs. saturated calomel electrode (SCE) in 3.5 wt% NaCl and artificial seawater solution. All these composite sacrificial anodes satisfy the protection criterion set by NACE (−0.778 V vs. SCE). The highest negative potential of −0.920 V vs. SCE has been obtained with the 0.9P-5Zn anode, which is close to the working potential of commercially available pure Zn anodes (the open-circuit potential of these anodes is about −1.10 V vs. SCE). The enhanced sacrificial nature of the composite anodes is associated with the formation of Fe3Zn10 intermetallic phase in the iron matrix after sintering. This results in the formation of micro-galvanic cells leading to the partial dissolution of Zn from the Fe3Zn10 intermetallic phase, which shifts the potential towards active values. Successful development would enable us to commercialize these composite sacrificial anodes using proper waste management of the high P pig iron and provides a sustainable solution to corrosion protection. This cost-effective approach is one of its kind where iron would protect iron in undergound and underwater applications. © 2025 Elsevier Ltd