(High Temperature Sealant)
Any lined vessel may be employed for sealing. Ceramic lined or stainless steel cooking pots are ideal. Do NOT use aluminium, as it causes problems.
Always use distilled water, as ordinary water may leave mineral deposits on/in the film.
Anodising Sealant is a nickel acetate compound for sealing anodic coatings on aluminium. Anodising Sealant is a fine flowing greenish powder, readily soluble in water. It is specifically formulated with a pH regulator and an agent to help minimize smut. Anodising Sealant is suitable for clear anodise and offers increased weather and light-fastness on coatings dyed with aluminium dyes.
Make up a solution of 7.5 grams of Anodising Sealant to 1 Litre of distilled water
Time: 5 to 30 minutes depending on anodise thickness (2-3 minutes per 0.10 thou oxide coating thickness) 24 microns = 1 thou. (The anodise film will grow at the rate of 0.10 thou every 3 minutes of anodising.)
pH: 5.5 to 6.0
Water: Deionised or Distilled water
CONDITIONS FOR USING ANODIZING SEALANT
Tank: Sealant solution should be contained in a non-metallic or ceramic lined steel tank.
pH: pH adjustments will not be necessary unless acetic or alkaline compounds are carried over into this sealing bath. Then acetic acid (to lower pH) or ammonia (to increase pH). (Acetic acid is difficult to come by, and it is preferable to discard the bath, especially as it has a limited shelf life anyway.)
Rinse: Before sealing, a thorough rinse is necessary to remove any foreign substances. After sealing, the work should be thoroughly rinsed at once, as is normal in nickel acetate sealing, before it is dried.
Filtration Filtration clears the bath of precipitates with interfering action. Filter through coffee filters after each use.
Maintenance: Bath life is 14-60 days dependent upon operating conditions and bath upkeep.
Freshly prepared nickel acetate sealant baths are clear green solutions. In use they become contaminated by precipitates and grow cloudy. If not removed, these contaminants can form deposits on the sealed surface. The effect can be due to the following: High pH (at pH values above 6.0, nickel acetate may be converted into soluble nickel hydroxide), hard water and entrained impurities.
The following measure can be taken to minimize this affect: Maintain pH value of 5.7 ± 0.3, through rinsing of anodised, dye or un-dyed work prior to sealing to prevent possible introduction of contaminants and filtration to clarify the bath and to prevent surface deposit formation
As mentioned the bath life will range from 14-60 days. This is due to contamination of the sealing bath and decrease in the active substance. A decrease on preventing smudging and an increase in smut may be noticed. Thus even when the bath concentration is strengthened regularly, the Anodising Sealant must be replaced from time to time.
The consumption of Anodising Sealant is calculated from the amount absorbed by the anodic film, the amount carried out of the bath and the amount of active ingredients inactivated by the introduction of foreign substances. Below is the average consumption of Anodising Sealant per unit area of sealed surface:
Absorption by the film 0.4 g/m2
Amount carried off . 3 g/m2 Consumption for strengthening additions 7.0 g/m2