Abstract: A mixture for preparation of protective and insulating coatings on metals and metal products which sticks well to metal surfaces, is resistant to high temperatures, has good electrical properties, and provides good heat removal. The mixture includes aluminum oxide, barium oxide, boron oxide, silicon oxide, and aluminum fluoride.

Abstract: Steel products may be coated with an insulating composition by a process which involves coating a uniform layer of finely ground glass powder on the steel and burning it at temperatures ranging from 700.degree.-1000.degree. C. Following, a paste comprising a mixture of the afore-mentioned glass, aluminum oxide and an evaporable liquid are deposited upon the burned coating, dried and burned again at 700.degree.-1000.degree. C.The resultant coatings adhere well to steel and resist temperatures as high as 860.degree. C., so suggesting then use for coating steel destined as a substitute for ceramic supports in electronic and hybrid microelectronic applications.