The effects of beta-quenching on the corrosion resistance and microstructure of Zircaloy-4 were studied by gravimetric and electrochemical methods. Zircaloy-4 specimens beta-quenched, namely, annealed in vacuum at $1000^\circ{C}$ for 15 min followed by cooling at a rate of $320^\circ{C}$/sec, exhibited a martensitic, basketweave structure. The oxidation rate of beta-quenched specimens in steam at $550^\circ{C}$ and $750^\circ{C}$ was lower than that of the alpha-annealed specimens. The increase in the weight gain of Zircaloy-4 specimens by oxidation at $550^\circ{C}$ followed a cubic rate law and at $750^\circ{C}$ followed parabolic rate law.
The corrosion current density was measured by use of the four point method from polarization curves in the non-Tafel region of corrosion potential. The corrosion rates of beta-quenched specimens in the aqueous solution of 2.2 ppm LiOH, 2000 ppm and 4000 ppm $H_3BO_3$ and 0.05 mol HCl were lower than those of the alpha-annealed specimens in the aqueous solutions. The corrosion rate of Zircaloy-4 in the presence of 2.2 ppm LiOH was greater than that in the presence of 2000 ppm and 4000 ppm $H_3BO_3$. The better corrosion resistance in high temperature steam and in room Temperature aqueous solutions containing LiOH, $H_3BO_3$ or HCl of beta-quenched Zircaloy-4 specimens is believed to be correlated with fine, continuous chain-like distribution of second phase particles and fine grain size in beta-quenched specimens as apposed to the distribution of coarse second phase particles and larger grain size in alpha-annealed specimens.
