mirror coating on steel for 400¦C

[soptic]

We would like to coat a steel substrate (316L) with a highly reflective (> 80%) metallic or dielectric coating for 400°C operating temperature and minimum degradation with time. Is an Al deposition with a SiO2 protection layer a good choice? Thank you in advance.

 

[JimMetalsCeramics]

How large is the component? SiO2 is not a likely candidate for protection on steel (expansion mismatch. Does the mirror surface see abrasion?

 

[soptic]

Jim,
The components are small mirrors (3 mm diameter) and will see no abrasion. Do you think we will still have expansion mismatch problems, considering that the SiO2 layer is thinner than 1 micron?

 

[JimMetalsCeramics]

Yes. SiO2 has an expansion of 2ppm/C. Steels are 16ppm/C. If you opt for a ceramic, I'd see if someone can sputter ZrO2 or a high expansion glass.