F. Feil, W. Fürbeth
Galvanotechnik 102 (2011) 1468-1479
Starting out with aqueous, commercially available silica nanoparticle dispersions and additives, totally inorganic thin protecfive coatings were formed on magnesium alloys AZ31 and AZ91. By repeating the coating process several fimes followed by thermal
sealing at moderate temperatures, coatings of up to 1.5flm thickness could be formed. Using various test electrolyte solufions, these coatings provided localised
corrosion protection for several days, although a significant underlying wide area corrosion was observed. As a result of residual porosity, electrolytes were able to diffuse through the coating and form corrosion products. Coatings based on acid-catalysed or acid-stabilised polymer solutions are in general less porous than coatings formed from particulate containing solutions. Sealing of dispersion coatings with purely inorganic polymer liquors provides a superior protective action for a given coating thickness. Longterm stability is improved by the use ofinorganic corrosion inhibitors.