Grain oriented steel strips are usually delivered with a thin inorganic coating applied on both surfaces, on top of the so called glass film layer formed during annealing. The coating thickness of 2 to 5 µm provides good electrical resistance simultaneously ensuring a high stacking factor. The coating allows to carry out the stress relief anneal of wound cores or punched laminations, usually performed at temperatures around 840° C. The coating is chemically resistant to all fluids it may come in contact with during processing. It is unaffected by, and in turn does not affect, the various types of oils used in transformers.

Insulation basis	Phosphate over glass film
Colour
Colour deviations are possible without effecting the properties	grey
Coated sides	both sides
Thickness of coating	2 µm - 5 µm
Insulation coating resistance at room temperature according to IEC 60404-11	> 10 Ω cm2 / lamination
Temperature capability under inert gas according to IEC 60404-12	840 °C / 2 h
Chemical resistance to transformer oil	good
Designation according to IEC 60404-1-1	EC-5-G
Designation according to ASTM A976	C-5 over C-2