| Abstract Scope |
Ferrous wear-resistant coatings on aluminum substrates can form unfavorable galvanic couples in chloride service, driving sacrificial substrate loss. We applied combinatorial mixed-elemental-powder directed energy deposition to twelve Fe–(15,25,35)Mn–(2,6)Al–(2,4)Cr–0.2C compositions and characterized phase evolution, dry-sliding wear, and potentiodynamic corrosion across the full matrix, with zero-resistance ammetry (ZRA) against A356 aluminum for compositions spanning the manganese range. Standard corrosion screening did not predict coupling behavior: Fe–15Mn–6Al–4Cr, the lowest-Icorr composition in the matrix (0.6 µm/yr, below A356 itself), coupled strongly cathodic, while Fe–35Mn–2Al–2Cr, with a twentyfold higher corrosion rate, coupled net anodic and suppressed substrate loss. Polarization-derived Ecorr proximity alone did not resolve polarity; resting open-circuit potentials were closer than scanned values suggested, and dissolution-rate asymmetry between coating and substrate appears to govern which member turns anodic. Manganese content links wear resistance, self-corrosion, and galvanic compatibility in opposing directions, making coupled-current screening a necessary complement to potentiodynamic characterization for coatings on aluminum substrates. |