Oxidation of electroless Ni–P coated AISI 430 alloy and effect of pre-reduction

Abstract

The oxidation behavior of electroless Ni–P coated AISI 430 alloy was investigated at 800 °C in moisture-saturated (~ 3% H2O) air. Effect of pre-reduction in dry hydrogen (Ar-3%H2) at 800 °C on the oxidation behavior of the Ni–P coated AISI 430 was also studied. Microstructure, chemical composition, and compound/oxide phase formation across the oxide layer were analyzed by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction techniques. Iron oxide Fe2NiO4 spinel along with other oxide and spinel phases are found in the multilayered oxide scale for both the Ni–P coated and pre-reduced Ni–P coated AISI 430 alloy. Ni–P coating crystallization and oxidation initiates the oxidation for the electroless sample. Ni3P and FeNi3 intermetallic compounds formed during reduction initiates the oxidation of the pre-reduced sample.