Corrosion inhibitors

One of the most important acid additives are corrosion inhibitors. A corrosion inhibitor is a chemical that slows the attack of acid corrosion on drill pipe, tubing or any other metal that the acid contacts during treatment. Corrosion can occur in tubulars under three circumstances; the presence of acid (for use in stimulation treatments), the presence of dissolved Carbon Dioxide in produced water, and the presence of Hydrogen Sulphide from produced Hydrocarbons or Sulphate Reducing Bacteria.
The introduction of an acid system to any well configuration increases the risk of a destructive reaction between at the interface of the acid and the tubulars. The presence of acid encourages the oxidation of Iron present, releasing Ferrous Iron from the tubulars, and the reduction of Hydrogen ions. The result is a fast erosion of the tubulars, causing pitting, and compromising the integrity of the well.
Using a corrosion inhibitor will serve to create a film at the surface of tubular, and therefore inhibit this electrochemical reaction. Corrosion inhibitors should be specific to each down hole environment, considering temperature, acid and protection time required (in the case of stimulation treatments), well components within the well configuration and the presence of any other compounds within the produced hydrocarbons.