The proper analysis of soil and water at the drainage site and its watershed should form the basis for selection of materials and types of pipe that should have been required service life. The main corrosion medium affecting drainage facilities is water and chemicals dissolved in or transported by water. Field and laboratory tests have been used to predict deterioration rates for a given environment. Materials used for drainage pipe include steel, aluminum, concrete, vitrified clay, stainless-steel, cast iron and plastic. Pipe protection measures include extra material thickness, coatings of various types, linings, and cathodic protection. Detection of corrosion-abrasion deterioration in culverts requires periodic inspection: at intervals of 10 or more years in less aggressive environments, and every 3 years in more aggressive environments. Trained inspectors should determine the nature of the electrolyte, flow rate, bedload, soil and water resistivity and ph, location, extent and type of corrosion, thickness loss, preventive measures used and reason for deficiencies. A rating system may be helpful and adequate records of all inspections should be kept. Several pipe protective measures are reviewed here. The broad assortment of repair techniques should be analyzed from standpoints of practicality, compatibility with existing installation, prospective performance and economics. Principles which must be considered in the location, design, construction and maintenance of culverts are discussed. These principles relate to the need for soil and water information, future changes in land and water use which could affect corrosion-abrasion rates, contract proposals which should include other pipe materials, the avoidance of galvanic couples, the consideration of clean sand, crushed stone or gravel for culvert bedding, the removal of corrosion causing materials from trenches, removal of obstructions within culverts, and the provision of access for personnel and equipment for inspection and maintenance. The selection of an anticorrosion system would include: hydrologic and hydraulic considerations, structural considerations, availability and suitability of pipe types and sizes for the site, and the durability of the commonly used drainage materials that are satisfactory for the first 3 steps.
Abstract