Why Use Cement Mortar Linings?
Cement linings create an excellent corrosion resistant lining for many reasons. The main factor is that high density cement linings have an extremely low absorbtion rate preventing the constant flow and oxygen to the substrate, preventing the surface from corrosion. Cement linings also raise the pH at the steel surface and moves the steel into a state of passivation by creating a very thin, stable oxide layer on the steel substrate, Fe3O4 or Fe2O3² that inhibits corrosion. For steel passivation to be maintained, complete pipe coverage or cement bonding to the pipe or tank is not required. A wet or moist environment is preferred for the lining application and overall performance. If cracks or holes develop in the cement mortar lining, the lining itself has the ability to self repair (autogeneous healing, calcification). It can also be easily repaired by the contractor with minimum preparation (sandblasting not required) or long periods of downtime.
In contrast, epoxy coating or glass-lining is a relatively new lining practice introduced to North America in the late 1970s. Epoxy is a dia-electric coating that prevents tank or pipe corrosion by creating an impermeable barrier between the steel surface and the water. However, for the coating to be effective it must fully adhere to the steel surface and be continuous. To ensure that the epoxy, bonds to the pipe or tank, stringent preparation of the steel and application of the epoxy to a dry surface are essential. Unlike cement mortar, epoxy / glass-linings cannot self-heal cracks or holes and due to the high level of preparation, quality assurance and quality control required for epoxy coatings their cost is typically 25-35% higher then that of a cement mortar lining.