Electrical steel varnishes are designed to enhance the behaviour of fully processed electrical steels. For grain-oriented grades, the main purpose is to provide increased surface insulation resistance by means of a thin inorganic coating. This type 5 coating is applied on top of the glass film (type 2), which is obtained in the high temperature annealing process step as a result of the reaction of the steel surface with the annealing separator.


The C5-G type varnish is a pigmented varnish, predominantly composed of phosphates. As well as its electrical insulation properties, this coating has the advantage of withstanding stress-relief annealing, which restores the magnetic properties of grain-oriented steels at the cut edges, for optimum steel performance. It is selected for its good adherence and ability to withstand normal punching and cutting operations. It does not affect and is unaffected by transformer oil. Typical gauges range from 2 to 4 m per side.


These coatings are used for grain-oriented fully processed grades. Particularly for power transformers, which require high efficiency and operate continuously, it is important to have a double coating system, with the phosphate layer on top of the glass film.

Recommendations for use

The raw materials used have a chemical composition both in liquid and cured varnish state which does not require specific protective measures during the processing of the coated steels or during use in a given application.

Brand correspondence

 EN 10342:2005ASTM A976:2008IEC/CEI 60404-1-1:2004ArcelorMittal-Code
C5-G EC-5-GC-5EC-5-GK

Coating properties

Chemical compositionInorganic
ArcelorMittal codeK24
Typical gauge (m/side)2 to 4
Typical insulation resistance (Ω.cm2/side)> 10
Main propertiesInsulation / Heat resistance

Insulation measurement: Franklin test according to the standard EN 60404-11:2013.


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All details provided in the ArcelorMittal Flat Carbon Europe S.A. catalogue are for information purposes only. ArcelorMittal Flat Carbon Europe S.A. reserves the right to change its product range at any time without prior notice.