Topic: Coating of Magnesium Cast Parts
Magnesium has become more and more important particularly in the automobile sector due to several of its excellent properties. The advantageous properties of this metal are described adequately in the technical literature: lighter than aluminium, very good hardness-weight-ratio, high resistance to impact, excellent dimensional stability to mention a few. The challenge for the coating company is the high reactivity and the corrosion susceptability of magnesium associated with it.
Due to its years of experience, the Heiche Group offers its customers considerable know-how on pre-treatment and coating.
The main points are:
Pre-treatment for adhesion
- Pre-treatment for painting
- Corrosion protection through cathodic dip-coating
- Corrosion protection or functionalisation of the surface through sol-gel coating (nano technology)
Pre-treatment for adhesion:
Using a process developed by the Heiche Group it is possible to activate magnesium-cast surfaces in such a way that an excellent bond between metal and wood veneers results, e.g., from phenolic resin.
Pre-treatment for painting:
The application and combination of various pre-treatment processes and conversion coatings assure excellent, corrosion-resistant bonding with powder and wet paint coatings.
Cathodic dip coating
Through the development of a pre-treatment process especially adjusted to the cathodic dip coating process, we succeeded in obtaining cathodic dip coating on magnesium cast with high corrosion protection: 240 h up to 1000 h in the salt spray test (depending on the cast quality)
Sol-gel coating
When the highest corrosion demands are made on magnesium parts, our constructed nano-sized, sol-gel coatings offer excellent protective functions. However, the synthesis variations possible in these sol-gel systems make possible further property profiles in addition to the corrosion protection, such as, e.g., hydrophoby, hydrophilicity, oleophoby, etc.
Property features
- Excellent adhesion
- Excellent corrosion protection (> 1000 h SSNT)
- Hydrophobic
- Resistant to mechanical stress
- Resistant to organic solvents
- Resistant to thermal stress (up to 250°C)
- Layer thicknesses of 2-20µ
It is important that the pre-treatment of the magnesium parts be adjusted to the sol-gel coating. In doing so, the excellent property profile of the sol-gel coating is further increased particularly with regard to adhesion and corrosion protection.
Most of the applications refer to the most common magnesium-cast-alloys AM50 and AZ91. Our development department will gladly check other cast alloys using sample coatings.
