Seawater corrosion testing cavitation

Titanium resists erosion—corrosion by fast-moving sand-laden water. In a high velocity, sand-laden seawater test (8.2 m/s) for a 60-d period, titanium performed more than 100 times better than 18 Cr—8 Ni stainless steel. Monel, or 70 Cu—30 Ni. Resistance to cavitation, ie, corrosion on surfaces exposed to high velocity Hquids, is better than by most other stmctural metals (34,35). 

The standard steels of the type SAE 316 (DIN-Mat. No. 1.4401, X5CrNiMol7-12-2) are not suitable for seawater-exposed pipes and fail as a result of pitting and crevice corrosion [155, 156]. The sensitivity to pitting corrosion of these standard steels can be further increased by deposits of maritime bacterial films [157]. Despite these facts, these steels are frequently used as materials for pump parts and have worked well as such because they are cathodically protected by contact with other parts made of less noble materials, e.g. pump casing made of cast iron [130]. [158] reports on tests of the cavitation behaviour of the pump materials GX5CrNiMol9-ll-2 (DIN-Mat. No. 1.4408) in 3% NaQ solution. 

Untersudiungen der Kavitationskorrosion an Pumpenwerkstoffen in Meerwasser (Tests of the cavitation corrosion in pump materials in seawater) (in German) Werkst. Korros. 33 (1982) 5, p. 288... 

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