Kester Acid-Cored Wire is a highly active, inorganic acid type of flux developed for general-purpose soldering applications where a flux-cored solder wire is desirable. Rapid soldering can be accomplished on all common metals except aluminum and manganese. Acid flux is particularly useful for soldering excessively oxidized metals. Acid Core possesses excellent thermal stability to function under prolonged high temperature conditions as with torch or flame soldering. It is not recommended for electrical or electronic soldering applications due to the corrosive nature of the residue. Acid Core is classified as INH1 per J-STD-004.