Articles protected against corrosion and methods for protecting articles against corrosion

Abstract

Steel articles are protected against corrosion by being completely or partially coated with a material showing a resistivity of at least 0.1 M.OMEGA..cm and comprising a matrix which comprises (A) inorganic solid particles of a size of from about 50 .ANG. to about 0.5 .mu.m, or a coherent structure formed from such homogeneously arranged particles, and (B) densely packed solid particles having a size of the order of 0.5-100 .mu.m and being at least one order of magnitude larger than the respective particles stated under (A), or a coherent structure formed from such densely packed particles, the particles B preferably being Portland cement particles. Particles A are preferably ultrafine silica particles formed by growth from vapor phase and are substantially densely packed in the voids between the particles B. Particles A are especially present in an amount of 10-30% by volume, calculated on the combined volume of the particles A+B. Composite material for forming the matrix typically comprises Portland cement, ultrafine silica, water in low proportion, and a concrete superplasticizer in high proportion, optionally with additional bodies such as fibers or mica, and is easily shapeable and also suitable for underwater application. Resistivity of the coating material is in the range of 0.3-10 M.OMEGA..cm, typically at least 1 M.OMEGA..cm. Development of resistivity accelerates when curing is performed at elevated temperature. Steel article may, e.g., be one in which the steel receives cathodic protection, or a pipe connector (10) which comprises a pair of axially spaced tubular bodies (11, 12) interconnected by said coating material (22).

Dependencies are inferred from the claim text.