ELECTRICAL MEASUREMENTS ON THE GROWING SCALE ON ZIRCONIUM-TITANIUM ALLOYS

The corrosion rates of low-titanium zirconium alloys increased with titanmum content when exposed to water at 290 deg C or to 1 atm oxygen at 290, 350, 400, and 500 deg C. The scaling rate reached a maxmmum (approximately 3000 at 500 deg C and then decreased with increasing titanium content. Under the same conditions, pure zirconium and tmtanium had much lower weight gains, 10 and 4 mg/ dm/sup 2/ respectively. In oxygen at 500 deg C, the oxidation rate law was initially cubic or parabolic for alloys containing 3.75, 15.0, and 50.0 at.% Ti, and then changed to approximately a linear one. The transition times were 17, 7, and 54 min for the in the rate law and the rise in EMF and resistance appeared to be independent variables. The electrical changes were attributed to changes in defect structure, and the rate law ansitions were attributed to structural channges. The reilts provided an explanation for the maximum oxidation ite at 15 at.% Ti and for the differences in the influence of dditives on the corrosion rates of zirconium and titanium in high temperature water. Thc EMIF of the corrosion cell consisting of STAalloy /oxide! O/sup 2/! was a function of the resistance of the oxide layer. The 3.75 and l5.0 at.% Ti alloys had small EMF's and resistances inittally, but EMF and resistance increased appreciably and rapidly at times after the transition stage. The 50 at.% Ti alloy had a very small EMF which was relatmvely constant while the resistance showed a slight increase with time. (auth