6.1 INTRODUCTION

Corrosion phenomena are well-known in the petroleum industry and cause a maximum damage to oilfield equipment. Significant corrosion protection efforts have been made by petrochemical industries to prevent corrosion damage. The practice of corrosion prevention by adding substances which can significantly retard corrosion when added in small amounts is called inhibition. Inhibition is used internally with carbon steel pipes and vessels as an economic control alternative to stainless steels and alloys, and to coatings on non-metallic components. One unique advantage is that adding inhibitor can be implemented without disruption of a process. The addition of an inhibitor (any reagent capable of converting an active corrosion process into a passive process) results in significant suppression of corrosion. Corrosion inhibitors are selected on the basis of solubility or dispersibility in the fluids which are to be inhibited. For instance, in a hydrocarbon system, a corrosion inhibitor soluble in hydrocarbon is used. Twophase systems composed of both hydrocarbons and water, utilize oil soluble water-dispersible inhibitors. Corrosion inhibitors are used in oil and gas exploration and production, petroleum refineries, chemical manufacturing, heavy manufacturing, water treatment and product additive industries. The total consumption of inhibitors in USA alone costs over one billion dollars annually.

6.2 SCOPE OF INHIBITOR

Corrosioncontrolbyuseofinhibitorsisextremely useful in many environments, however, there are certain exceptions, such as:

1. equipment and components subjected to turbulent flow.

2. systems operating above the stability limits of inhibitor.

3. equipment subjected to high velocity, beyond 4 m/s.

However, adding inhibitors can raise the value of the critical...