Investigation of Synergistic Effects of Some Organic Inhibitors With Nitrate Ion On The Corrosion of Mild Steel In Ethylene Glycol-Water Solution

摘要

Ethylene glycol (EG) has been a popular coolant in chillers. Pure ethylene glycol freezes at about -12°C, but when mixed with water molecules, neither can readily form a solid crystal structure, and therefore the freezing point of the mixture is depressed significantly. Therefore it is ideally used as an antifreeze in the cooling systems of the internal cumbustion engines of automobiles. Inhibitors are used to control the corrosive effects of cooling media on the system. Inhibitors are organic or inorganic materials that slow down or block the metallic corrosion process. The aim of this study is to investigate the synergic effect of some organic materials in the control of corrosion by inorganic inhibitors in the ethylene glycol-water cooling media in the automobile coolant systems. In this field of study the synergic effect of inorganic and some organic materials containing -OH, -NH_2 and -S groups has been investigated. The inhibition effect of amido black 10B on the corrosion of mild steel in 40 vol% ethylene glycol solutions sodium nitrate beside synergistic effects of amido black10B and some newly synthesized Schiff bases was studied using potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and linear polarization resistance techniques. In this study 0,5 M Na_2SO_4 has been used as supporting electrolyte. N03- concenration were kept constant at 10~(-2) M and organic inhibitor concenrations were varied from 10~(-4) M to 10~(-2) M. Impedance diagrams of studied inhibitors with amido black 10B are given in the Fig.1. The obtained results showed that the addition efficiency of amido black 10B and sodium nitrate together in 40 vol% ethylene glycol solution reduces the corrosion rate of mild steel. The inhibition efficiency increases with amido black 10B concentration and reached a value of 57 % at 10~(-2) M concentration. Similar results were obtained on other Schiff bases.