Abstract: A process for treating spent fluoride-containing pickling paste on metal surfaces by applying to the spent pickling paste on the metal surface an aqueous treating paste composition comprising calcium carbonate having a particle size not in excess of about 5 microns and an alkali metal bicarbonate, which composition has a pH which is not in excess of about 9.5.

Abstract: A pickling and rust-removing paste composition suitable for cleaning metal surfaces, including surfaces of steel and aluminum. The composition contains fluoride ions and a mixture of calcium compounds and tervalent iron and/or aluminum compounds and has an acidity corresponding to at least 10% by weight of free acid, calculated at 100% HF. The composition also most preferably contains at least one anion selected from nitrate, sulfate, phosphate and chloride and has an acidity corresponding to from about 15 to 30% by weight of free acid, calculated as 100% HF.The composition is applied to that portion of the metal surface, such as steel or aluminum, to be treated and is retained in contact with the surface for a period of time sufficient to effect the desired pickling and/or removal of rust on the surface.

Abstract: Disclosed is a corrosion inhibitor for metal surfaces. The surface is contacted with an alkaline aqueous solution containing a reaction product of an aliphatic carboxylic acid, a polyhydroxy carboxylic acid and an alkanol amine.

Abstract: Disclosed is a composition and process for inhibiting an aqueous acid solution and a composition so inhibited. The acid solution containing, for example, HF is inhibited by including a condensation product of a mixture of diethyl- and dibutyl-thiourea with hexamethylenetetramine.