Effect of Benzotriazole on the Hydrogen Absorption by Iron

The results presented show that benzotriazole (BTA) inhibits the absorption of hydrogen into iron which is cathodically polarized in an acid (pH ≅ 1.7) sulfate solution. Analysis of the results indicates that BTA inhibits also the hydrogen evolution reaction, although it does not change its mechanism, which is shown to be proton discharge‐Tafel recombination. However, BTA shifts the position of the equilibrium, , toward the left side and hence leads to a decrease in the concentration of within the lattice. The extent of this decrease depends on the BTA concentration, e.g. , about fivefold at 1 m M and tenfold at 10 m M BTA. This effect is opposite to that reported for inhibitors such as thiourea which inhibits the hydrogen evolution reaction and yet promotes hydrogen permeation.