The acid etching technique uses dilute phosphoric acid that decalcifies or etches the enamel to result in an increased surface area and enables adhesion. The technique is used in adhesive restoration process as it enhances the micromechanical retention of fissure sealant on the tooth and prevents dental caries. In the amalgam filling of the cavities, acid etching allows the maximum retention of the composite resin. It also finds application in dental surgery and in the treatment of dental problems arising from hypoplasia and hypomineralization (during the placement of dental veneers).
A combined solution of ferric chloride and hydrochloric acid is used as the etchant in the jewelry industry to etch copper, brass, and bronze, but not silver. The resist area is protected from etchant by coating with enamel or paint. Electrolytic etching and electroplating methods also utilizes this technique. The acids used in metal etching are ammonium-per-sulfate (for brass and copper), ferric chloride (for steel, brass, and copper, but not in zinc as the process emanates explosive hydrogen gas bubbles), and a mixture of sodium chloride and copper sulfate (for iron, zinc, and aluminum).
Acid etching is used in the manufacturing unit of glasses to make a frosted pattern on glass surfaces. Glasses for decorative purposes are etched with acid prior to the process of gilding. The artists immerse the stenciled glass in acid tank (hydrofluoric acid is used only for deep-etching process as it is hazardous) for efficient etching.
In any overlaying or resurfacing procedure performed in the concrete floors of homes, shops and garages, acid etching helps to roughen and prepare the concrete surface to facilitate good bonding of the coating material. The concrete floor is treated with acid (hydrochloric or muriatic acid, phosphoric acid, or sulfamic acid) and etched before the application of the coating system.