Abstract
Acid washing is a commonly employed method in the chemical cleaning. There are many factors to consider prior to adding acid to a given system. For example, corrosion of the base materials, downtime of the system, and the economic cost of completing the job. None of these factors can be considered separately; therefore, a strong understanding of the chemical cleaning process is necessary for maintaining efficiency. The addition of wetting agents, intended to reduce the surface tension between the cleaning solution and the deposit, is also believed to increase the rate of dissolution by allowing more of the chemical to reach the scale surface. However, very little data exists regarding the actual rate constants, contact angles, and ultimately the efficiency of individual surfactant blends on the actual reaction rates. A frequently encountered scale is calcium carbonate, CaCO3. A number of commercially available surfactants were added to different acids and the rates for the dissolution of CaCO3 were compared at various temperatures. Surfactants representative of the four major types of wetting agents, (cationic, anionic, amphoteric, and non-ionic) were examined, and comparisons are drawn as to the efficiency of wetting of each type, with respect to the observed rate of dissolution of the scale and the measured contact angles.
