Cathodic protection of aluminum generally requires small current densities, e.g., roughly 10 times less than the current requirement for steel in seawater. Potentiostatic tests carried out in flowing natural seawater with selected alloys in the 1000, 5000, and 6000 series indicate that this results from the destruction of cathodic sites on the surface after the onset of cathodic protection. This occurs by crevice corrosion of the matrix adjacent to the cathodic intermetallic particles and detachment of particles from the surface without exposing new ones from the bulk matrix. The exposed matrix area is quickly covered by a protective oxide film. Formation of more continuous insulating oxide leads to an improved passivity. The steady-state current requirement is normally of the order of a few mA/m2 and independent of the flow rate. Although calcareous deposits are detected, these are thought to play a minor role in the polarization of the surface.
Cathodic protection of aluminum in seawater
Kathodischer Schutz von Aluminium in Meerwasser
Corrosion, Houston ; 46 , 4 ; 279-285
1990
7 Seiten, 9 Bilder, 2 Tabellen, 17 Quellen
Article (Journal)
English
Cathodic protection in cold seawater - Current density requirements
Tema Archive | 2009
|Internal cathodic protection of seawater piping by the RCP method
Tema Archive | 1996
|Localized cathodic protection of simulated prestressed concrete pilings in seawater
Tema Archive | 1995
|Effects of cathodic protection on duplex stainless steels in seawater
Tema Archive | 1997
|Cathodic protection against crevice corrosion of high-alloy steel in seawater
Tema Archive | 1995
|