Anaum Nawaz, Kashif M. Deen,Ameeq Farooq, Rafiq Ahmed,I. H. Khan Department of Metallurgy & Materials Engineering, CEET, University of the Punjab, Lahore, Pakistan Predicting the corrosion tendency of a-brass in acidic and alkaline tapwater This study focuses on the electrochemical behavior of brass in acidicand alkaline tap water. Both conditionswere stu- died using corrosion potential,cyclic polarization and elec- trochemical impedance spectroscopy. Weight loss experi- ments were also performed tovalidate corrosion behavior. It was evaluated from corrosion potentialvaluesand Pour- baix diagrams that brass surface was aggressively attacked at low pH due to dissolution of zinc-rich phase and solva- tion of cuprite and zincate at high pH by breakdown of the passive film. Under near neutral conditionsthe increase in charge transferresistance corresponded to formation of a stable passive film. Brass exhibited peculiar behavior at pH 1 and 12 by showing lowcharge transferresistancedue topreferential attack of zincand solvation of copper/zinc rich phases, respectively,asvalidated by impedance spec- troscopy. Keywords: Brass; pH; Electrochemical; Corrosion; Impe- dance spectroscopy 1. Introduction Copper metalhas awide range of application due toits out- standing properties. Copperand its alloys are extensively used in the manufacturing of water treatmentunits, conden- sers, desalination, heat exchangers and processing plants for electricity generation [1, 2]. Brasses are the most promi- nent among copper-based alloys which are extensively used in cooling water systems because of their excellentthermal conductivity, strength, weight and appearance [3]. The brasseswith 20 wt.% to 36 wt.% Zn contents how- ever are susceptible to selective corrosion and pitting when one element or constituent is preferentiallyremoved as a consequence of corrosion processes called dezincification. It occurs when the metalis exposed to acidic orsalt med- ium. This type of corrosion usually occurs when brass is in contactwith seawater orwithfresh waterthat have high oxygen and/or carbon dioxide content. Dezincification in- volves dissolution of the alloy and a subsequent deposition of porous non-adherent copper [4– 7]. The process of zinc dissolution leadsto serious deterioration of the surface and mechanicalproperties of the alloy. Water is a good solvent, whichhas good ability to dis- solve most of the salts and inorganic substances. The pre- sence of many ions in water increases corrosion problems in cooling systems. In the past, major failures have been re- ported due the aggressive anions in cycliccooling water. The water corrosiveness varies largely on its composition and type of alloy exposed toit [8, 9]. In cooling water sys- temsthe aggressive ions, such as chloride, sulphate and large amount of dissolved oxygen, can break the passive film on a-brass [10]. Chloride ions are the main species in cyclic waterresponsible for corrosion damages. Inorderto minimizefailures in cooling water equipment and suggest preventive measures, it is essential to studythe corrosion mechanism of these ions on brass surface [9–14]. Inmany research works, the corrosion behavior of brass in tap water, sodium chloride, hydrochloric acid solutions and natural seawater has been investigated individuallywithorwithout inhibition [15 – 18]. Howeverthe previous work on brass dealswith the determination of corrosion inhibition byvar- ious organicand/or inorganic species in acidic or neutral conditions. But the corrosiveness of alkaline solutionsto- ward brass has not been discussed in detail. In thiswork, the effect of increase in hydrogen and/or hy- droxyl ion concentration on corrosion behavior of alpha brass has been explored at pH from 1 to12.The results of thisresearch work were correlated thermodynamicallywith the potential–pH diagram of copper/zincand validated ki- netically by means of electrochemical methods, i. e. corro- sion potential,cyclic polarization and electrochemical im- pedance spectroscopy (EIS). 2. Experimental procedure Commercialgrade brass (67 wt.% Cu, 33 wt.% Zn) samples (L= 50 mm; w = 25 mm) and (L= 75 mm; w =40 mm) were cut from 0.75 mm thick sheet forweight loss determi- nation and electrochemical testing respectively. For micro- structuralevaluation 1 cm 2 specimenswere wet ground from 120 to 2 000 gritsize silicon carbide papers followed by polishing on cloth impregnated with diamond paste (1 lm). To reveal microstructural detailsthe specimen was etched in 50vol.% HNO 3 solution [19]. Weight-loss measurements were carried out by immer- sing samples of known dimensions and weightseparately in 300 ml tap water having pH ranging from pH 1 to12 ad- justed bythe addition of hydrochloric acid (HCl) and 1 N sodiumhydroxide solution (NaOH)from pH 1 to pH 6 (acidic) and pH 8 to pH 12 (alkaline) respectively atroom temperature. The sampleswere taken out from the solutions after 15, 30 and 45 days exposure. These were cleaned in 3vol.% H 2 SO 4 solutionsto remove any loose corrosion product, rinsed in distilled water and dried in air. Triplicate specimenswere tested to validate the corrosion behavior of IJMR_MK111153 – 7.10.14/stm media köthen A. Nawaz et al.:Predicting the corrosion tendency of a-brass in acidicand alkaline tap water 1