Abstract
Problem statement: The effect of different temperatures and acid concentrations on the corrosion of low carbon steel in hydrochloric acid were addressed in this study. Approach: The effect of temperature was explained by application of Arrhenius equation and transition state theory, while the acid concentration effect was explained using reaction kinetic equations. The combined effect of temperature and acid concentration then modeled using a nonlinear regression method. Results: A detail of thermodynamic parameters of activation (E, ΔH* and ΔS*) and kinetic studies for the corrosion reaction were obtained. Nonlinear corrosion rates as a function of temperature and acid concentration equation were estimated with a good prediction corrosion rates values. Conclusion: The values of activation energy E and enthalpy of activation ΔH* decrease with increase in acid concentration indicating the increasing in reaction rate. Entropy of activation ΔS* tend to lower values with increasing in acid concentration which indicated that the activated complex was more orderly relative to the initial state. The corrosion reaction was approximately firs order reaction. The observed corrosion rate values from the experimental data were in a good agreement with that predicated by the mathematical equation.
Highlights
Steel is one of the major construction materials, which is extensively used in chemical and allied industries for the handling of acid, alkali and salt solutions
The aim of this study is to study the effect of temperature and acid concentration using Arrhenius Equation transition state equation and reaction rate kinetic equations on the corrosion of low carbon steel in HCl acid
The values of ∆H* was 90.708 at 1 M acid concentration. This value decrease with increasing in acid concentration, which indicate that the reaction need low energy to occur with increasing of acid concentration. This mean that the energy barrier of corrosion reaction decrease as the concentration of hydrochloric acid increase and activated complex or transition state complex can be formed faster with acid concentration increasing
Summary
Steel is one of the major construction materials, which is extensively used in chemical and allied industries for the handling of acid, alkali and salt solutions. Hydrochloric acid is the most difficult of the common acids to handle from the standpoints of corrosion and materials of constructions. Extreme care is required in the selection of materials to handle the acid by itself, even in relatively dilute concentrations or in process solutions containing appreciable amount of hydrochloric acid. This acid is very corrosive to most of the common metals and alloys. The wide use of this acid has led to the concentration of this study on the corrosive effects of this acid on carbon steel, which is a versatile component in many industrial structures
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