5.1 Selection of corrosion inhibitor for oilfield and refinery applications involves qualification of corrosion inhibitors in the laboratory (see Guide G170). Field conditions should be simulated in the laboratory in a fast and cost-effective manner.

5.2 Oilfield and refinery corrosion inhibitors should provide protection over a range of flow conditions from stagnant to that found during typical production conditions. The inhibitors are not equally effective over all flow conditions, so it is important to determine the flow conditions in which they are effective.

5.3 Severity of hydrodynamic conditions depends on the type of laboratory methodology. Typically, rotating cylinder electrode is effective up to 20 Pa of wall shear stress, rotating cage (RC) is effective between 20 and 200 Pa of wall shear stress, and jet impingement (JI) is effective at wall shear stress above 200 Pa (1)3 of wall shear stress.

5.4 The JI test system is relatively inexpensive and uses simple flat specimens.

5.5 In this practice, a general procedure is presented to obtain reproducible results using JI simulating the effects of different types of coupon materials; inhibitor concentrations; oil, gas, and brine compositions; temperature; pressure; and flow. Erosive effects predominate when the flow rate is very high (typically above 500 Pa) or when sand or solid particles are present; however, this practice does not cover the erosive effects.