Abstract: Acidic hydrosols are provided for forming an electrically insulating and corrosion resistant coating on a substrate which consumes a minor quantity of acid from said hydrosol, said substrate being selected from the group consisting of metals higher than hydrogen in the electromotive series, porcelain, glass, wood, paper, cotton, plastics and hydrateable oxides.The hydrosols of this invention are formed by admixing water, an acid such as phosphoric acid, or nitric acid, or hydrochloric acid or acetic acid or mixtures thereof, a metal silicate or hydrous magnesium silicate, and optionally, a magnesium compound and a boron compound. A significant feature of the present hydrosols is their water-white clarity and resistance to deterioration or decompositin for at least 15-20 minutes, and their ability to deposit a substantially uniform coating virtually instantaneously upon said substrates when placed in contact therewith.

Abstract: Magnesium oxide coating compositions, process for their preparation and process for applying said compositions as adherent dried coatings which when annealed form relatively non-porous insulations providing improved electrical insulating properties. The coating compositions comprise a major proportion of magnesium oxide and a minor proportion of zinc permanganate and magnesium sulfate, wherein the concentration of zinc permanganate is from about 4 to about 16 parts per 100 parts of magnesium oxide and the concentration of magnesium sulfate is at least about 50 parts per 100 parts of zinc permanganate.