Influence of the PH value of the medium on the inhibition of corrosion in steel modified by polyhexamethylene guanidines

It is shown that the corrosion rate of steel in the presence of polyhexamethylene guanidines decreases as the concentration of polyelectrolytes increases (this effect is more pronounced in acid media). The modification of polyhexamethylene guanidine with carboxylic and phosphonic groups leads to an increase in its inhibiting effect and, moreover, the polyhexamethylene guanidine modified by phosphonic groups exhibits quite high inhibiting properties under the conditions of corrosion of steel in alkaline media, which is explained by its polyampholytic properties. The comparison of these results with the corresponding adsorption isotherms reveals the adsorption nature of the inhibiting effect of polyelectrolytes. It is shown that the inhibiting effect of polyhexamethylene guanidine modified by phosphonic groups is connected with the blocking model. In the other cases, we observe deviations from this model, which possibly can be explained by the action of activation and conformation factors.