9 - Corrosion and protection of aluminum alloys in seawater

Abstract

Publisher Summary This chapter focuses on the corrosion and protection of aluminum alloys in seawater. Corrosion of aluminum alloys under exposure to one-phase flow, even under highly turbulent conditions, is a mass transfer controlled phenomenon. Use of aluminum alloys in seawater is of continuous interest because of the need for light-weight structural materials. As long as galvanic contact with more noble metals is avoided, most structural alloys, such as those in the AA1000 (commercially pure), 3000 (AlMn), 5000 (AlMg), and 6000 (AlMgSi) series, are resistant to corrosion in seawater, especially the so-called seawater-resistant alloys in the 5000-series. Under stagnant and low flow-rate conditions, uniform corrosion rate lies below 1 µm/y. Crevice corrosion is normally not a problem for aluminum alloys. However, it is observed in joints and it is basically a design problem like galvanic corrosion. Pitting, flow-dependent corrosion, and erosion–corrosion are the basic corrosion problems for aluminum alloys in seawater. The chapter reviews the danger and mechanisms of these corrosion types and possible protection methods, especially cathodic protection.