Chromatographic and iron carbonate dissolution methods for evaluating active ingredients in corrosion inhibitors

Three new methods for inhibitor evaluation are described. The first method utilizes measurements of the dissolution rate of iron(II) carbonate in the presence of the inhibitor. The remaining two methods rely upon measurements of gas and liquid chromatographic retention times on columns that are packed with iron(II) carbonate. All three methods assume that an iron carbonate scale protects the underlying metal from corrosion. The methods were tested by using linear amines as test inhibitors and by comparing the results to weight loss measurements. Although the methods do provide adequate results for pure amines, the use of commercial inhibitor mixtures with the chromatographic methods sometimes proved unsatisfactory.