IOSR Journal of Applied Physics (IOSR-JAP) e-ISSN: 2278-4861, PP 49-57 www.iosrjournals.org National Conference on Current Advancements in Physics 3 rd &4 th February 2017 49 | Page Department of Physics, St. John’s College, Palayamkottai-627 002, Tamilnadu, India. DOI 10.9790/4861-17002024957 Galvanic Corrosion Characteristics of Aluminium Alloy with Group II Metal Vijayarani K a , VishnuDevan M a , and Natarajan R b . a P.G.& Research Department of Chemistry,Government Arts college,Karur ,690005,Tamil Nadu. b P.G.& Research Department of Chemistry, Alagappa Government Arts college,Karaikudi-630003,Tamil Nadu. Abstract: The Electrochemical behavior of Al -Zn5% sacrificial anode with selected element (Sr) has been investigated in 3% sodium chloride solution. Corrosion experiment was mounted to determine the optimal effect of Sr on the efficiencies of the aluminium alloy anodes. The unexposed sample was subjected to micro structure characterization by SEM and XRD techniques. The impedance measurement and microscopic observation confirmed that better activity was realized with Al-Zn-Sr alloy compared with base Al-Zn5% alloy. The addition of Sr shifts open circuit potential (~ 50 mV) and corrosion potential (~ 60 mV) to a negative value. However, the shift is observed as a gradual decrease with Strontium content and 5% of strontium addition resulted with maximum efficiency (99.46%). Better electrochemical performance of Al–Zn–Sr5% alloy attributed as due to the presence of fine grains Al 2 Zn 3 Sr 3 and grain boundaries that contains fine Al 2 Zn 3 Sr 3 precipitate. The addition of Sr improves the electrochemical properties of Al90–Zn5–Sr5 % alloy and resulted uniform corrosion due to the presence of fine grains of particles constituent elements with distribution of these particles across the grain boundaries. The electrode is very efficient in the view of economical point of view and can be prepared conveniently as a conventional hanging electrodes, tolerable in very aggressive media and high efficient under high current load. Keywords: alkaline earth metal, aluminium alloy, efficiency, sacrificial anode and strontium. I. Introduction Corrosion is the deterioration of materials with its environment and it can be mitigated by various techniques. Cathodic protection is one of the techniques that are employed mainly in industries and marine environments to control corrosion. Cathodic protection is greatly employed to protect oil pipelines, marine and some industrial structures. In this system, particularly sacrificial anode system, electric current is applied by using dissimilar metals with the driving voltage created by the potential generation between the two metals in an electrolyte system. The electrochemical behaviour of sacrificial anode materials is of vital importance for the reliability and efficiency of cathodic protection systems [1]. Generally, metals such as aluminium, zinc and magnesium are employed as anode materials in sacrificial cathodic protection systems. The limitation of usage of magnesium based alloy system is its low efficiency, which gives rise to loss of substantial parts of the required current capacity. It is affirmed that aluminium is the most preferred sacrificial anodes for controlling and preventing corrosion in marine environments. Aluminium anodes are also favoured over zinc anodes for the cathodic protection of offshore structures especially in deep water exploration because they are lighter and less expensive. Evaluation of the performance of aluminium anodes is necessary to achieve the most cost-effective sacrificial cathodic protection design. The usefulness of pure aluminium as an anode material in seawater is reduced significantly due to the formation of a protective oxide film, which limits both its current and potential output. In order to improve the efficiency of aluminium anodes they are typically alloyed with other elements to encourage depassivation (breakdown of the oxide film) and/or shift the operating potential of the metal to a more electronegative direction. The alloying elements used to accomplish this are referred as depassivators and modifiers. Modifiers that have been used in practice include zinc, magnesium, barium, and cadmium. Also, the depassivators commonly used are indium, mercury, tin and rarely gallium, titanium and thallium. However, these metals are highly toxic in marine environment. Hence, the metal modifier used should possess eco-friendly as well as good activation for an improved performance as sacrificial anodes. Most of the efforts in this field were carried out using aluminium rich zinc sacrificial anodes and the concentration of zinc in aluminium alloy sacrificial anodes has been optimized to 5 wt% due to high improvement in metallurgical and electrochemical properties of the alloy through the formation of β-phase [2] Addition of alloying elements like tin and indium shifts the potential of the anode in the negative direction and helps in keeping the anode active [3]. Modification of Al + 5%Zn alloy anode is essential due to non-columbic loss and low galvanic efficiency [4] The base alloy chosen for the present work is Al + 5%Zn, which has been