Materials Sciences and Applications, 2014, 5, 10-19 Published Online January 2014 (http://www.scirp.org/journal/msa ) http://dx.doi.org/10.4236/msa.2014.51002 Electrochemical and Stress Corrosion Cracking Behavior of Alpha-Al Bronze in Sulfide-Polluted Salt Water: Effect of Environmentally-Friendly Additives Elsayed A. Ashour 1* , Lobna A. Khorshed 1 , Gehan I. Youssef 1 , Hossam M. Zakria 2 , Tarek A. Khalifa 2 1 Electrochemistry Laboratory, Physical Chemistry Department, National Research Centre, Dokki, Cairo, Egypt; 2 Mechanical Engi- neering Department, Faculty of Engineering at Shoubra, Benha University, Cairo, Egypt. Email: * easshour@yahoo.com Received October 22 nd , 2013; revised November 27 th , 2013; accepted December 19 th , 2013 Copyright © 2014 Elsayed A. Ashour et al. This is an open access article distributed under the Creative Commons Attribution Li- cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In accordance of the Creative Commons Attribution License all Copyrights © 2014 are reserved for SCIRP and the owner of the intel- lectual property Elsayed A. Ashour et al. All Copyright © 2014 are guarded by law and by SCIRP as a guardian. ABSTRACT The stress corrosion cracking (SCC) behavior of α-Al bronze alloy (Cu 7 Al) was investigated in 3.5% NaCl solu- tion in the absence and in the presence of different concentrations of Na 2 S under open circuit potentials using the constant slow strain rate technique. Also, the addition of different concentrations of cysteine (cys), and alanine (ala) to the test solution, as corrosion inhibitors, was studied. Increasing the sulfide ions concentration in pol- luted salt water resulted in a reduction in the maximum stress (σ max ) and an increase in the susceptibility of α-Al bronze towards SCC. The addition of ala and cys to the test electrolyte increased the time to failure by changing the mode of failure from brittle transgranular cracking to ductile failure. Electrochemical tests were performed to assist the interpretation of the SCC data. Electrochemical impedance spectroscopy (EIS) was used to investi- gate the mechanism of corrosion inhibition. The results support film rupture and anodic dissolution at slip steps as the operating mechanism of the SCC process. Therefore, cys and ala can be considered as potential envi- ronmentally-friendly corrosion inhibitors for the SCC of α-Al bronze in 3.5% NaCl solution containing sulfide ions. KEYWORDS Bronze; Sulfide; Corrosion; SCC; Inhibitor; Amino Acids 1. Introduction Copper-base alloys have a long history of service in ma- rine environments. Aluminum bronzes contain copper as the major component and aluminum as a minor compo- nent. They have good strength [1-6] and superior resis- tance to cavitation erosion and impingement attack [7]. Al-bronzes have been used in various sea water applica- tions [1,8-10], the manufacturing of acid handling equip- ment, and dental restoration [2]. Small quantities of Fe, Ni, or Ag may be added to Al-bronzes to improve their corrosion resistance and mechanical properties [1-4]. The corrosion resistance was attributed to the formation of a thin film of Al 2 O 3 , which heals rapidly when dam- aged [11-13]. The corrosion resistance of Al-bronze in- creases with increasing the aluminum content up to about 9.6%, which represents the limit of the ∞-phase [14]. Beyond that limit, the two-phase alloys undergo severe corrosion and loss of ductility, which had been attributed to selective loss of aluminum [10,15-17] i.e. dealumini- fication. In this regard, the electrochemical and stress corrosion cracking (SCC) behavior of Al-bronzes has been reported in marine and desalination environments [18-20] and in 3.4% NaCl solutions [13]. Various pollutants, such as nitrite ions [18], are often introduced in the work environments, which might have a delirious effect on the workability of such alloys [19]. More seriously, the presence of sulfide ions in seawater, from seaweed, sulfide reduced bacteria, or industrial * Corresponding author. OPEN ACCESS MSA