Sealing/ Dichromate Sealing
About sealing
When anodisation is performed, pores are formed in the aluminium product that need to be closed in order for the product to achieve optimum sealing, weather-resistance and aesthetic appearance.
Sealing "closes” the surface so that water becomes chemically bonded to the anodiation layer during formation of the crystal Böhmit.
Sealing
When sealing is performed, the surface absorbs water so that the pores are sealed and the surface becomes sealed.
The process takes place in water at 98°C where the water becomes chemically bonded to the anodisation layer during formation of the crystal Böhmit.
Sealing in water is performed as standard when anodising, but is a process that can be opted out of. For example if the surface is to be painted or bonded.
Dichromate Sealing
In order to maximise the corrosion protection, anodised products can be dichromate sealed.
Dichromate sealing is a chemical chrome compound that also seals the built up anodisation layer. When this process is performed chrome is absorbed into the surface.
The process is not usually used for decorative application as the surface becomes irisating yellow (dark green) and it is not possible to subsequently colour the product.