Corrosion 

CHAPTER ONE

INTRODUCTION

Corrosion is the deterioration of materials. Corrosion is a natural phenomenon and almost all the metals corrode or are expected to deteriorate with time. For example, iron rusts when exposed to moisture, copper tarnishes and aluminum acquires a whitish, hydrated oxide film. Corrosion is regularly encountered, for example, in the chemical, petrochemical and food processing industries, in air, sea and rail road transportations, in conventional and nuclear power generations, in building and construction industries, in agriculture and in numerous domestic application.

The driving force that makes metals corrode is a consequence of their temporary existence in the metallic or refined state, contrary to their natural, stable form, as ores. Thus, corrosion is a reversion, or partial reversion, from the metal state to the more stable mineral state. When there is a difference in potentials of metals exposed in the same environment, the metal higher in the series i.e. the metal  with low potential difference will corrode and protect the one lower in the series.  Hence, this work seeks to investigate electrode potentials of local available metals and their   comparison in terms of corrosion. For a metal to corrode, there must be three factors to be present, – cathode, anode, electrolyte and external circuit.

In electrochemistry, the standard electrode potential, abbreviated E⁰,  E^o or E^q   (with a superscript potential, abbreviated E⁰,  E^o or E^q   (with a superscript phunisoll character, pronounced nought, is the measure of individual potential of a reversible electrode (at equilibrium) at standard state, which is with solute at an effective concentration of I mol/kg, and gases at a pressure of 1 bar. The values are most often tabulated at 25^oC. The basis for an electrochemical cell such as the galvanic cell is always a redox reaction which can be broken down to two half reactions: oxidation at the anode (loss of electron) and reduction at the cathode (gain of electron). The potential difference is created as a result of the difference between individual potentials of the two metal electrodes with respect to the electrolytes.

1.1    Statement of the problem

A part from the physical, chemical and mechanical properties of metals that are seriously affected in  corrosion processes! The loss of metals and the cost of the consequences of corrosion are very high in any industrial country. When an oxide forms on a metal surface the amount of metal ion remaining is obviously reduces and if this is under load the stress acting on it will raised. The same is true if the metal is being dissolved. In either case, if the ultimate tensil stress (UTS) is exceeded, then the specimen will break. Not every student is familiar with the mechanism of corrosion as a natural phenomenon. Hence, the investigation to elucidate how metals could be joint or connected together in construction or fabrication in terms of their electrode potentials in order to minimize corrosion.

1.2    The objectives of the work

Corrosion, nevertheless, constitutes a real burden to industries and huge financial losses are regularly incurred. Hence, the need of this work to fully elucidate the mechanism of this undesirable processes and subsequently determine the necessary preventive measures and distinguish the effectiveness in the use of the electrochemical series to determine the electrode potential of locally available metals for construction as one of the most effective methods of corrosion control. And to save as a teaching aid in the classroom.

1.3    Scope of the Work

The work is concern with the measurement of electrode potentials of locally available metals for construction.

• Introduction
• Literature Review
• Materials and Method
• Results and Discussion
• Conclusion and Recommendation

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