Benzotriazole derivatives as inhibitors of iron acid corrosion.

Derivatives of the benzotriazole (BTA) molecule, with an alkyl chain in position 5 of the aromatic moiety, have been proved as inhibitors of pure (Armco) iron corrosion in 1N sulphuric or hydrochloric acid at 25 °C. The alkyl chain was 1 , 4 , 6 , 8 or 12 carbon atoms long. Positive results were afforded by compounds with an aliphatic chain as long as 6-8 carbon atoms. Generally, the greater the number of carbon atoms in the alkyl chain, the higher the inhibiting performances and the longer the persistency of the inhibiting action, but since a long aliphatic chain decreased the compound solubility, the maximum inhibiting effects produced by the dodecyl derivative were not as high as those of the hexyl or octyl derivatives. The inhibiting action was higher in the hydrochloric acid solution than in the sulphuric one, and this evidenced a phisi-sorption mechanism between the protonated organic molecules and the chloride ions adsorbed on the iron surface. Nevertheless, a certain chemisorption effect has to be taken into consideration, since a persistent protective action was also found on inhibited coupons immersed in non-inhibited solutions.