Problems in ship painting

Modern methods of cleaning do not always remove variations in the surface condition of steel, and the old corrosion patterns sometimes reappear after careful impact cleaning. Possibly this is caused by hammering rust into the surface, but more probably residual contaminants such as sulphates are responsible. Since it is unlikely that any cleaning method will remove all effects of previous corrosion, the choice of primer is important. Clearly, it is a dangerous practice to use a low‐quality ‘temporary primer’ which allows rusting during construction, unless the ship is to be re‐blasted and coated with a high‐quality primer.