Abstract
The aim of this paper is to analyze the corrosion process that occurs in galvanic couplings of different alloys. The study focuses on materials that can come into contact in submersible pumps used by water treatment plants. Because, the rotor, one of the pump main components must possess high chemical and mechanical properties, nodular cast iron is usually used. Therefore, this is exposed in the same environment with different types of materials, such as aluminum, copper, bronze, grey cast iron, low alloy steel or stainless steel from which other components are made. The tests have been performed in three types of residual waters with neutral, acidic and basic pH. According to this study, the nodular cast iron galvanic corrosion resistance is highly improved by the phosphate layer deposited on its surface.
Highlights
The aim of this paper is to analyze the corrosion process that occurs in galvanic couplings of different alloys
It can be appreciated that the nodular cast iron in coupling with many metals or alloys will function as an anode and will undergo an advanced corrosion process [4]
The difference between the corrosion potentials is not a sufficient criterion to predict a certain degree of galvanic corrosion, this difference expresses only the thermodynamic probability of the occurrence of the galvanic corrosion but it does not highlight anything about the kinetics of the process, meaning the corrosion rate [5, 11-24]
Summary
The aim of this paper is to analyze the corrosion process that occurs in galvanic couplings of different alloys. The rotor, one of the pump main components must possess high chemical and mechanical properties, nodular cast iron is usually used This is exposed in the same environment with different types of materials, such as aluminum, copper, bronze, grey cast iron, low alloy steel or stainless steel from which other components are made. The cast iron and the nodular cast iron, in particular, have quite large negative electrode potentials so that in any galvanic series these are located between the most electronegative metals, lower than these being only aluminum alloys, zinc or magnesium On this basis, it can be appreciated that the nodular cast iron in coupling with many metals or alloys will function as an anode and will undergo an advanced corrosion process [4]. The severity of bimetallic corrosion depends on several factors that can influence the reaction rate, such as temperature, electrolyte composition, pH, the ratio of the areas of the two metals of the couple etc. [6]
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