Corrosion rates of binary alloys of nickel and iron measured by polarization methods

Specimens of ten binary alloys of nickel and iron containing 3, 5, 10, 16, 20,30,36,50 ,57, and 81 percent Ni and of the metals nic kel and iron were immersed for 7 months in 265 gallons of c ity water to which had been added 3 percent by weight of sodium chloride. Cathodic and anodic polarization curves of the specimens were obtained at about 22 periodic intervals throughout the exposure period. Corrosion currents, calculated from curre nts at break s in the curves, were converted to corrosion rates e xpressed as weight losses by applying Farad ay's law. The calculated weight losses were in reasonable agreement with the actual we ight losses. The polarization rates, /lV/M , of the spec ime ns calc ulated from ca thodic polarization curves (cathodic control pre vailed) at several intervals throughout the ex pos ure period were plotted on logarithmic coordinates with respec t to the corrosion curre nt de ns ities calculated from breaks in the same curves . S imilarly, the ave rages of these /lV/M valu es we re also plotted on logarithmic coordinates versus the actua l corrosion rates ex pressed as weight losses. Both plots conformed to the theoretical slope of 1.