Hydrogen Absorption by and Dissolution Rate Of Low-Carbon Steel In Sulfuric, Hydrochloric, Phosphoric and Nitric Acids

The dissolution rate of steel in 2 N and 10N solutions of nitric acid at 100 F (38 C) was much faster than for the same concentrations of the other acids studied, although for 0.05 N and 0.5 N solutions the rate was not significantly different than that for sulfuric acid. Dissolution in H2SO4 solutions of 0.5 N and 2 N at 100 F was more rapid than dissolution in hydrochloric acid, but for 10N acid the rate in HCl was greater than for H2SO4. Dissolution rates in phosphoric acid solutions at 100 F were slower over the entire concentration range than for other acids at comparable concentrations. The dissolution rates in 2 N acid solutions increased with an increase in temperature. The amount of hydrogen introduced into the steel during dissolution in HNO3 solutions was much lower than for the other acids. Although the dissolution rates at 100 F differ between H2SO4, HCl and H3PO4 solutions at the various concentration levels, the percentage of theoretically available hydrogen absorbed by the steel after a given weight loss did not differ significantly between these three acids. For each acid, particularly when the weight loss was low, the amount of hydrogen absorbed at a given weight loss decreased with increase in temperature.