NACE TM0397-2012

The test methods described in this standard are static laboratory screening tests designed to measure the ability of chemicals to remove gypsum scale deposits. There are two types of scale-removal chemicals: dissolvers and converters. Scale dissolvers, generally chelating or sequestering agents, can affect the dissolution and removal of gypsum scale in one step. Converters, such as those formulations based on sodium (or potassium) glycolate and sodium (or ammonium) carbonate (or bicarbonate), are used to alter or convert the calcium sulfate to another compound which is then removed by dissolution with a dilute mineral acid (typically hydrochloric acid). Test methods for screening both gypsum scale dissolvers and converters are described.

These test methods are recommended only for ranking the performance of different scale-removal chemicals under the laboratory conditions set by these test methods.