Corrosion Rates of Ductile Iron Pipe in Drilling Fluids: A Comparison of ASTM Electrochemical Standards G59, G102, and G106 to ASTM Weight Loss Standard G162

摘要

One of the most commonly used piping materials for transport of water and wastewater in the United States is ductile iron pipe (DIP). Although this piping normally is installed using open trench cuts, a trenchless installation method that is finding increased popularity for DIP is horizontal directional drilling (HDD). Many HDD installations utilize specialized drilling fluids, commonly called "drilling muds," which may be composed of bentonite clay, various organic and inorganic additives, polymers, lubricants, wetting agents, or polymers mixed with water (or any combination thereof). To evaluate the corrosion characteristics of these fluids in contact with DIP, a 1-year corrosion study involving more than 200 ductile iron pipe specimens was conducted comparing five commercially available directional drilling fluids. Corrosion tests were conducted using electrochemical test methods described in ASTM G59, Standard Test Method for Conducting Potentiodynamic Polarization Resistance Measurements, ASTM G102, Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements, and ASTM G106, Standard Practice for Verification of Algorithm and Equipment for Electrochemical Impedance Measurements, and these results were compared to 1-year weight loss test results obtained using ASTM G162, Standard Practice for Conducting and Evaluating Laboratory Corrosions Tests in Soils. This paper discusses which electrochemical test method and method of analysis gave results closest to those obtained with ASTM G162 weight loss evaluation.