Cement mortar is successfully used for the coating of underground pipe lines. It exhibits remarkable insulating properties in withstanding the galvanic forces of underground corrosion circuits. The particular features of the mortar, as a compound electrolytic conductor are considered. A practical method for resistivity measurements is suggested. Corrosive conditions are analyzed. Preventive measures and the criteria for cathodic protection are discussed.
It was found that a portland cement coating owes its protective properties to: (1) Corrosion inhibiting properties, (2) a noble half-cell potential, (3) self-sealing effect, and (4) rise of insulation resistance with the ageing of the line. The mortar coating was found especially suitable for large diameter pipes because of these ageing effects.
The use of bituminous coatings over mortar is discussed briefly. 5.4.2
