Corrosion resistance of Fe77Mo5P9C7.5B1.5 in-situ metallic glass matrix composites

Highlights: • A novel in-situ Fe-based metallic glass matrix composite was successfully produced. • The Fe₇₇Mo₅P₉C_7.5B_1.5 MGMC had lower corrosion resistance than a stainless steel. • The EDS analysis of the corroded Fe-MGMC revealed the formation of a passive layer. • The preferential dissolution of α-Fe dendrites was observed for the corroded MGMC. A novel in-situ Fe-based metallic glass matrix composite with a composition of Fe₇₇Mo₅P₉C_7.5B_1.5 was developed by injection casting. Scanning electron microscopy (SEM) and X-Ray diffraction (XRD) confirmed the presence of α-Fe dendrites as a secondary phase across the glassy matrix. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were utilized to study the corrosion behavior of Fe₇₇Mo₅P₉C_7.5B_1.5 in deaerated 1 M HCl solution and to compare it with that obtained for AISI Type 301 stainless steel as a Fe-base crystalline alloy. The electrochemical characterizations showed the lower corrosion resistance of the synthesized Fe-MGMC which was due to the galvanic cells formed between α-Fe dendrites and the glassy matrix. Energy dispersive spectroscopy (EDS) analysis of the corroded Fe-MGMC revealed the role of B and C in forming a passive layer mirrored by a stable vertical line in the anodic part of the corresponding potentiodynamic polarization curve. Although, the stainless steel sample yielded a lower corrosion rate and a higher charge transfer resistance, a passive-transpassive transition was observed in its anodic polarization curve confirming the lower stability of the passive film formed on the specimen. The preferential dissolution of α-Fe dendrites and formation of micro-sized pits were the characteristic corroded surface morphology of Fe₇₇Mo₅P₉C_7.5B_1.5 and AISI Type 301 stainless steel, respectively.