Influence de la salissure marine sur la corrosion des métaux et moyens de prévention

Ingénieurs à E.D.F., Service Etudes et Projets Thermiques et Nucléaires (S.E.P.T.E.N.)

Résumé

With the number of coastal power stations growing rapidly (see Fig. 1), Electricité de France has stepped up research effort on marine pollution, resulting metal corrosion and anti-corrosion techniques. Conditions vary widely from site to site and tailored solutions must therefore be found for each. Research on a general level is nevertheless possible e.g. on the main types of contaminant and the way they affect the corrosion behaviour of metals. Protective methods aim at preventing pollution or at minimising pollution effects. Application of antifoul coatings and chlorination of circuit water are examples of chemical protection techniques (fig. 2). Mode of chlorine dosing and the advantages and disadvantages of various chlorine production methods are discussed. Physical protection techniques include continuous mechanical cleaning of tubes (Fig. 3), filtration (Fig. 4, 5, 6, 7) and sea-water heating (Fig. 8). Details of equipment used are given. Plant design aims principally at providing sufficient flow velocities in pipes and heat-exchangers to prevent deposits of scale or living organims. If water sand-content is likely to be high, it may be advisable to insert a settling basin between the water intake and the filtration and pumping station.