The synergistic inhibitive effect and the thermodynamic parameters of 2 (2- hydroxylstyryl) pyridinium-N- ethyl iodide and some metal cations on the acid corrosion of low-carbon steel

The synergistic effect of 2(2-hydroxy styryl) pyridinium -N- ethyl iodide (cyanine dye) and some selected metal cations viz. Zn+2 or Cr+3 on the corrosion of low carbon steel in 2M H2SO4 has been studied by weight loss measurements and galvanostitic polarization technique over the temperature range 30 to 60°C. The efficiency of combined inhibitor was studied for different concentrations of Zn+2 and Cr+3 cations ranging from 5 10-3 to 10-1 M. The obtained results showed that the presence of cyanine dye molecules in the corrosive medium (2M H2SO4 solution) inhibits the corrosion process of lowcarbon steel and as the concentration of the cyanine dye increases the inhibition efficiency also increased at all the examined temperatures. The presence of Zn+2 ions only in the corrosive medium is not favorable for the corrosion of the steel metal but the presence of Cr+3 gives a higher inhibition effect. On the other hand, the presence of Zn+2 or Cr+3 ions together with the cyanine dye increases the inhibition efficiency at all examined concentrations and temperatures, while the synergistic effect of cyanine dye and Cr+3 ions is the best one. The activation energy, heat of adsorption and thermodynamic parameters of the synergistic effect of cyanine dye and metal cations under investigation on the corrosion process have been calculated at the different temperatures, supporting the obtained results. The electronic energies and charge densities for cyanine dye compound were calculated by the MINDO/3 method.