High Corrosion Resistance of Chromium-Bearing Amorphous Iron Alloys in Neutral and Acidic Solutions Containing Chloride

The corrosion resistance of amorphous iron alloys, whose practical application is expected because of their outstanding mechanical properties, has been studied by total immersion tests and electrochemical methods in acidic and neutral solutions containing chloride. In a 1N NaCl solution at 30 C, 0.01-1N HCl solutions at 30 C and in 6% FeCl₃ solutions at 40 and 60 C, the amorphous Fe-Cr-P-C and Fe-Cr-Ni-P-C alloys did not suffer pitting corrosion, and no weight losses were detected on the alloys containing 8 At% or more chromium using a microbalance after exposure for 168 hours. The polarization curves of the amorphous alloys did not exhibit the critical potential for pitting, and no anodic current densities higher than 10^-7 A/cm² were observed over the potential range 0 to 0.5 V(SCE) in 1N NaCl and 0 to 0.9 V(SCE) in 1M H₂SO₄ by potentiostatic anodic polarization of the alloys containing 8 At% or more chromium. The high corrosion resistance of the amorphous iron alloys results partly from the presence of chromium and large amounts of phosphorus and partly from a homogeneous single phase amorphous structure.