A complete evaluation program was designed to review the various types of lining systems that are presently available in North America for municipal pipeline internal coating application. These systems included 100% solids polyurethanes, ceramic epoxies, and polyethylene used for the internal protection of potable water and wastewater mains. Key performance properties of the lining systems were reviewed and tested, together with handling and safety characteristics. The behavior of the two 100% solids polyurethanes was excellent not only in all tests but in their handling and safety characteristics as well. Polyethylenes were good in many tests such as impact resistance and-abrasion resistance, but performed poorly in the cathodic disbandment test. Even though the ceramic epoxy showed relatively good chemical resistance and undercutting resistance, its poor adhesion, low impact resistance and brittleness raised concerns about its ability t(s provide long term corrosion protection in aggressive sewer applications.
Corrosion is considered to be the major reason for structure failures. The loss of the structure is serious enough in its self, but the unscheduled loss adds synergistically to operating expenses in the form of lost production or, worse, the loss of life and property from a corrosion-induced accident. In many instances, the most and perhaps the only effective measure that can be taken for corrosion control is to protect the structure with a coating. The coating acts as a barrier to prevent chemical compounds and/or corrosion current from contacting the structural material. Many variables are involved in achieving a desired life of the protection by a coating system such as substrate, environment, surface preparation, coating properties, as well as application method. Coating selection is recognized as a difficult, yet important process.
Corrosion control by coatings has progressed to a scientific level. This allows engineers and utilities to make reliable predictions and selections regarding specific corrosive conditions and coatings and to use a selected coating to prevent corrosion. Results of various performance laboratory tests on different coating systems are playing a major role in this exercise. Such performance results form the basis in establishing their correlation with field performance, predicting the long term life expectancy of the protection.
100% solids polyurethane, ceramic epoxies, and polyethylene are three lining systems that have been widely used in protecting structures made of steel, ductile iron, and concrete from internal corrosion, particularly in potable water and tough sewer pipe applications. 100% solids polyurethane and polyethylene are suitable for both potable water and waster water applications, while ceramic epoxies are being used for waste water service only. The progressive evolution in the choice of the above three coating systems for a specific application is usually based on one hand, on the accumulation of the experience acquired in the field, and, on the other hand, on knowledge of the products available. This information can be obtained first from data furnished by product suppliers. Many end users, however, often find that it is impossible to rely solely on individual supplier?s data. This is mainly due to: 1) results of a proprietary test being done by one supplier may not be available from other product suppliers; 2) different test methods have been used; and 3) there are many varieties of tests giving results which cannot easily be compared.
During the course of the past five years, a complete evaluation program has been conducted for Madison by three independent laboratories which specialize i
