Effect of Sodium Tungstate, Sodium Molybdate and Thiourea on Corrosion of Aluminum in Oxalic Acid Solution

Abstract

 Corrosion of aluminum in oxalic acid had been investigated by using wt-
loss technique in absence and in presence of 0.001 M concentration of different

additive compounds (sodium tungstate [ST], sodium molybdate [SM] and
thiourea [TU]) at different temperature. It is noticed from the observed
thermodynamic parameters derived from wt-loss measurements that ∆Had for the
adsorption of ST, SM, and TU resulted in a positive value (endothermic), the
adsorption typed is physical - chemical adsorption. The dissolution of aluminum
in oxalic acid is decreasing as the concentration of the acid increased due to the
collective properties of organic acid were the oxalic acid behave as dimmer
molecular at different concentration. The dissolution of aluminum in oxalic acid
decreased after short period due to fast formation of oxide passive layer
[Al2O3.3H2O].