Wastewater corrosion protection is a major problem for municipalities worldwide. Every year, hundreds of millions of dollars are lost to wastewater concrete corrosion and the failure of H2S corrosion protection on a very wide range of structures, including pump stations, wet wells, plant influent structures, sedimentation tanks and many varieties of conveyance structures within the conveyance and treatment systems of every large city in the world. Most wastewater corrosion protection has become ineffective since most large cities began enclosing their collection and treatment structures in the 1970's. Although the problem is essentially a biological problem, the main failings of the materials used for wastewater corrosion protection can be reduced to 2 main problems.
Wastewater coating systems typically do not fail because of their chemical makeup, but rather due to the environmental conditions which are inherent in working on wastewater structures in an H2S corrosion protection application. Those conditions are constantly changing, minute by minute, as the substrate "breathes" vapor and corrosives through the liquid applied coating. The coating itself may be very well-designed, but the coating design cannot change the environment in which it must be applied. Usually, the contractor has a great deal of difficulty controlling this environment as well. The resulting wastewater concrete corrosion develops behind the wastewater coating system due to permeability that is inherent in the application method, rather than contractor error or faulty coating materials. Liquid applied materials rank very poorly as H2S corrosion protection due primarily to this problem.
Wastewater lining systems typically fail due to lateral migration of corrosive Hydrogen Sulfide and thiobacillus, rather than permeability. Colonization of the thiobacillus actually causes wastewater concrete corrosion behind the liner where the fastening mechanism is located. You will find a great deal of information on successive pages regarding these problems and how you can defeat them on your own projects involving wastewater corrosion protection.