Metal surface preparation tips

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

“…105 It has been pointed out that, of the several groups who have been working on cerium coatings, all use fairly standard degreasing and deoxidation steps as pretreatments. 118 More exotic surface treatments, such as plasma, have been investigated, 132 but with little success to date. It is not clear, however, that these would achieve acceptance over existing pretreatments without offering significant process or performance advantages.…”

“…80 The group at the University of Missouri-Rolla (UMR) have reported the formation of satisfactory Ce coatings on AA 7075 by electrolytic deposition, 144 spray 109,110,148 and immersion, using alkaline cleaning as the only pretreatment. 144,147,148 This did not work with AA 2024, 132 although alkaline cleaning has been noted to have relatively little effect on the surface of AA 2024. 51 The UMR claimed that including a deoxidation step overetched the surface and affected the rate of deposition and performance of the coating, [145][146][147] and as acceptable coatings could be deposited without the use of any additional process steps, 144 it appears that efforts to incorporate them were abandoned, at least temporarily (see the section on 'Base etching').…”

“…The alloys that have been most widely investigated with regard to rare earth coating are the aerospace alloys1 AA 202410,17,31 – 33,38,51,58-60,77,94-135 and AA 7075 8,12,13,31,32,77,79,102,105,112,114,…”

“…In a similar way, cerium processes also require pretreatment, as cerium will generally not deposit on an as received surface, even on an active alloy like AA 2024,51 and the surface must normally be stripped back before coating can take place. Surface preparation also influences both the degree of Ce deposition58,96,102 and the coating performance,132,147 particularly on different alloys 41,42. The work in Australia by CSIRO and the Defence Science and Technology Organisation (DSTO) with Boeing in the early 1990s was based on the view that rare earth coatings could be improved by altering the pretreatment,121 an idea that was later extended in work with BAE Systems77,126,193 and Lockheed-Martin 194.…”

Influence of Aerospace Standard Surface Pretreatment on the Intermetallic Phases and CeCC of 2024-T3 Al-Cu Alloy

“…However, as stated in an extensive review [15], there are still uncertainties in this technology that limit its commercial use. One of the gaps detected is that relatively little work has been carried out regarding the effect of pretreatments on the Ce coating, even though it is well known that pretreatments alter the morphology and chemistry of the alloy surface, and subsequently affect the deposition process and the properties of the Ce-based layer [16][17][18][19][20].…”