CORROSION BEHAVIOR AND INHIBITIVE EFFECTS OF ORGANOTIN COMPOUNDS ON NICKEL IN FORMIC-ACID

Corrosion behavior of nickel (Ni) in different compositions of formic acid (HCOOH) at 30-degrees-C was studied using the potentiostatic pola rization method. The shape of the polarization curve was evaluated, an d the corrosion current density, critical current density, and passive current density were determined HCOOH solutions of different composit ion were aggressive for the anodic dissolution of Ni, except for 20 an d 30 mol/O HCOOH, in which feeble passitivity was observed. The organo metallic compounds dibutyltin dichloride, phenyltin trichloride, diphe nyltin dichloride, and triphenyltin chloride ([C6H5]3SnCl) reduced the corrosion rate of Ni in 20 mol/O and 40 mol/O HCOOH. (C6H5)3SnCl was the most efficient. Inhibitive action was explained on the basis of ad sorption following the Langmuir adsorption isotherm, with the highest surface coverage given by (C6H5)3SnCl. The inhibitive action of organo metallic compounds toward Ni in HCOOH was caused by the phenyl group a nd delocalized pi electrons.