CYANINE DYES AS CORROSION-INHIBITORS .3. THE EFFECT OF THE MOLECULAR-STRUCTURE OF CYANINE DYE ON THE CORROSION OF LOW-CARBON STEEL IN HYDROCHLORIC-ACID SOLUTION

The effect of two different cyanine dyes 2-(2-hydroxystyryl)quinoliniu m-1-ethyl iodide (I) and 4-(2-hydroxystyryl)quinolinium-1-ethyl iodide (II) on the electrochemical corrosion behaviour of low-carbon steel ( 0.05% C, 0.04% Si, 0.023% S, 0.004% Cu) in HCl solution has been studi ed. Weight loss measurements, galvanostatic polarization curves, open- circuit potential variation of steel electrode with time and the catho dic protective current values show that the investigated cyanine dyes have an anticorrosive character. The inhibition effect depends mainly on the structure of the studied dye molecules, and is more pronounced in case of pretreated carbon steel with the dye solution before immers ion in the corrosion medium than that obtained by addition of the dye to the corrosive medium.