Galvanic corrosion inhibition behavior of coupled copper—Steel alloys in cooling water system Aprael S. Yaro a , Anees A. Khadom b, *, Munaf A. Idan a a Chemical Engineering Department, College of Engineering, University of Baghdad, Aljadrea,Baghdad, Iraq b Chemical Engineering Department, College of Engineering, University of Diyala, Baquba City, Diyala, Iraq A R T I C L E I N F O Article history: Received 30 May 2014 Received in revised form 8 September 2014 Accepted 10 September 2014 Keywords: Corrosion test Electrochemical techniques Adsorption Alloys Computer modeling and simulation A B S T R A C T The purpose of this paper is to evaluate the electrochemical galvanic behavior of corrosion inhibition of the copper alloy–mild steel couple which exposed to cooling water. Polyvinyl alcohol inhibition behavior has been evaluated under different operating conditions. Weight loss and polarization techniques have been used to evaluate the corrosion rate kinetics. The inhibition efficiency increases with increasing concentration of inhibitor. Maximum inhibitor efficiency was 86% at 7000 ppm inhibitor concentration and 1:1 anode to cathode ration. The experimental data fit Langmuir isotherm. Mathematical analyses were used to correlate the variables. Quantum chemical parameters were calculated using the PM3-SCF method. ã 2014 Elsevier Ltd. All rights reserved. Introduction The design of many industrial units and equipment is directly or indirectly determined by considering corrosion or corrosion control problems. The increasing demands being placed on structures and equipment have led to the requirement of using a combination of materials to obtain the desired performance. Galvanic corrosion is often the unfortunate result. In such cases, the corrosion is stimulated by the potential difference that exists between the two metals, the more noble material acting as a cathode where some oxidizing species is reduced, the more active metal, which corrodes, acting as the anode. The galvanic corrosion rates and the potential distribution over a galvanic couple, in general, depend upon the electrochemical properties of the metals, on environmental variables such as temperature, salinity, oxygen content, and solution flow, as well as the geometry of the corroding system. The severity of an attack depends on the conditions [1]. Cooling water system is one of the most important industrial units. The aim of this work is to evaluate the electrochemical behavior of corrosion inhibition of the copper alloy/mild steel galvanic couple expose to simulated cooling water. Polyvinyl alcohol (PVA) was utilized to evaluate the inhibition behavior under galvanic conditions. Inhibitor concentration, the cathode/anode (C/A) area ratios, and distance between anodic and cathodic elements in galvanic system were the variables of research. Polyvinyl alcohol (PVA), a colorless, water-soluble synthetic resin employed principally in the treating of textiles, paper and as a corrosion inhibitor [2,3]. PVA has a relatively simple chemical structure with a pendant hydroxyl group. The chemical structure of the polyvinyl alcohol is Experimental work Materials and methods Corrosion rate of copper alloy/mild steel couple in the absence and presence 1000, 4000, and 7000 ppm of polyvinyl alcohol (PVA) as corrosion inhibitor, area ratios (C\\A) of 1:1 and 2.4:1, the distance between copper alloy as cathode and mild steel as anode was 3 and 7 cm at room temperature and at static conditions were carried out. Two alloys were used in present work as a couple. Mild steel (SA515GR6) with two sizes (4.9  3  0.3 cm and 2.83  3  0.3 cm) supplied by the Ministry of Oil – Al-Dura Refinery. The second electrode was a copper alloy type ASTM B-111-443 with one size (3.5  4.43  0.2 cm). The chemical compositions of both alloys are listed in Table 1. The corrosion environment was industrial water used in the cooling system of Al-Dura Refinery with specifications listed in Table 2. The specimens were first degreased with analar benzene and acetone, and then annealed in a vacuum at 600  C for 1 h, and cooled to room temperature. * Corresponding author. Tel.: +964 790 2305786. E-mail addresses: aneesdr@gmail.com, aneesdr@yahoo.com (A.A. Khadom). http://dx.doi.org/10.1016/j.jece.2014.09.009 2213-3437/ ã 2014 Elsevier Ltd. All rights reserved. Journal of Environmental Chemical Engineering 2 (2014) 2120–2128 Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/je ce