Copper has excellent electrical and thermal conductivity and is often used in heating and cooling systems. Scale and corrosion products cause a decrease in the heating efficacy of the equipment, which is why periodic descaling and cleaning in acid-pickling solutions are necessary. Corrosion inhibitors protect from the destructive effect of the acid on such equipment. Most acid corrosion inhibitors are nitrogen-, sulfur-, or oxygen-containing organic compounds. Imidazole derivatives are of interest as corrosion inhibitors for metals and alloys. [1][2][3][4][5][6][7][8][9][10][11] Imidazole is a heterocyclic organic compound with two nitrogen atoms forming part of a five-membered ring. 12 One of the nitrogen atoms is of the pyrrole type and the other is a pyridine-like nitrogen atom.In our previous paper we investigated the efficiency of imidazole and its derivatives 4-methylimidazole, 4-methyl-5-hydroxyimidazole, 1-phenyl-4-methylimidazole, and 1-(p-tolyl)-4-methylimidazole (Fig. 1) as copper corrosion inhibitors in HCl, and we discussed three possible mechanisms for corrosion inhibitions by these molecules. We have recently investigated the temperature dependence of the corrosion current and obtained activation energy for the corrosion processes. In addition, we have studied the nature of the inhibitor adsorption processes. These studies indicate that these inhibitors are physisorbed to the copper surface. The results of these investigations are reported here. Experimental Materials.-Concentrated HCl (Merck), HNO 3 (Merck), and imidazole (Aldrich) were used as received. The inhibitors 4methylimidazole, 4-methyl-5-hydroxymethylimidazole, 1-phenyl-4methylimidazole, and 1-(p-tolyl)-4-methylimidazole were obtained from the pharmaceutical company Pliva (Zagreb, Croatia). Ethanol (Merck) and purified water (Millipore) were used to rinse the samples. The copper working electrode was of 99.98% purity.Methods.-Potentiodynamic experiments were conducted at 20, 30, 35, and 45ЊC using an EG&G Princeton Applied Research model 263A potentiostat/galvanostat and controlled with EG&G corrosion analysis software model 352/252 SoftCorr. A conventional threeelectrode electrochemical cell of volume ϳ100 mL was used. The working electrode was prepared from a cylindrical copper rod insulated with polytetrafluoroethylene tape such that the area exposed to solution was 0.785 cm 2 . A saturated calomel electrode (SCE) was used as the reference; a Pt plate electrode was used as the counter. All potentials are reported vs. SCE.
Corrosion is defined as the destruction of metals and alloys by chemical or electrochemical reaction with its environment. The corrosion occurs because of the normal trend of metals to come back to their thermodynamically stable native state. Corrosion cannot be avoided, but it can be controlled and prevented by using suitable methods like cathodic protection, anodic protection, metallic coating, alloying and using inhibitors, etc. Of these, the application of inhibitors reduces the aggressiveness of the corrosive and unsafe aqueous surroundings and preventing the metal and alloy from corrosion by forming a protective layer over the metal surface. The corrosion behavior of stainless steel and other metals in seawater has been studied by many researchers [1-2]. Stainless steels (316L) have been used successfully in many applications in the marine environment. 316L is considered to be one of the most resistant of stainless steel under marine environments, and it has excellent mechanical properties at elevated temperatures and easy fabricability. It is an important structural material for many industrial units, especially the desalination plants. 316L is the most likely candidate for saline environment applications due to their excellent corrosion resistance. The present work was undertaken to study the corrosion behavior of SS 316L metal in different mediums such as Seawater and calcium chloride (Fig. 1) solution by polarization study. The effect of oxygen or air in the electrolyte solution will also be investigated. Corrosion parameters such as corrosion potential, corrosion current, linear polarization resistance, and corrosion rate will be compared and presented in the meeting. References [1] Baoping Cai et al., Corrosion Science 52 (2010) 3235–3242 [2] Yong Cui et al., Water Research 88 (2016) 816-825 Figure 1
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