These coatings have been specially developed to minimize the degradation of the graphite structure in the rim-zone of CGI castings. Without such preventative measures, there is the risk of the formation of a flake graphite containing skin that can have a thickness of typically up to 1mm, or in some more, which will affect both the mechanical properties and the machinability of the casting.
During the casting process, a depletion of magnesium within the solidifying skin of the casting can occur due to reactions of the magnesium with sulphur and oxygen present in the moulding materials and/or in the mould atmosphere. This combined with the under-cooling effects at the metal/mould interface can lead to a reduction in compacted graphite formation in favour of flake graphite.
ACTICOTE CG coatings act to provide a barrier to core gases and reduce under-cooling, reducing the affected reversion layer to a minimum. Additionally, the coatings have high performance benefits including:
+ The refractory filler is highly resistant to the high temperature of the liquid iron and has good insulation properties.
+ The coating is formulated with excellent rheological properties making it ideal for the dipping of cores, building the required layer thickness without runs or drips.
+ The water-based coating has optimal drying properties without any spalling or the formation of craters or blisters, ensuring the cast surface is free from pin-holes, blemishes or scabs.