Cerium-based conversion coatings on aluminium alloys: a process review

Rare earths are among the most promising options for replacing chromate conversion coatings on aluminium. In nearly three decades of research, several hundred papers have been published in the area, the bulk of which has never been reviewed. This paper reviews the literature on rare earth coating processes, with particular emphasis on those based on cerium. It is concluded that several process areas are poorly understood, some of which are critical to further progress in the field. These include the development of industrially suitable pretreatments, technologies for coating non-aerospace alloys and seals to enhance corrosion performance and paint adhesion.