IRON CORROSION INHIBITION IN HOT 4-M HCL SOLUTION BY T-CINNAMALDEHYDEAND ITS STRUCTURE-RELATED COMPOUNDS

The inhibiting action of t-cinnamaldehyde (TCA) and some of its struct ure-related derivatives, against corrosion of ARMCO iron in 4 M HCl, h as been studied, in the temperature range between 40 and 90 degrees C. Other than TCA, alpha-chlorocinnamaldehyde (alpha Cl), alpha-bromocin namaldehyde (alpha Br), cinnamyl alcohol (OH) and cinnamnitrile (CN) h ave been considered. The average corrosion rates and the inhibiting ef ficiencies have been calculated by weight loss measurements at the end of 6-h tests; the dissolution kinetics have been determined on aliquo ts, by spectrophotometric analysis of the dissolved iron during the 6- h testing. The anodic and cathodic polarisation curves have been recor ded in all the tested conditions, at the end of the 6-h tests with the purpose of obtaining some information on the action mechanisms of the inhibitors. CN and TCA are the best inhibitors, showing efficiencies >94% in the whole interval of temperature examined. CN seems to act ma inly through a chemisorption process, whereas in the case of TCA the a dsorption process is followed by some polymerisation-reduction reactio ns.