4. Finishes, treatments and controls

4.1 Chemical machining

Parts are dipped in a bath of nitric acid and hydrofluoric acid (fluonitric bath) at a temperature of around 40-50°C to increase its aggressiveness. The faster the attack, the better the surface finish obtained. The action of additives incorporated into the acids (surfactants), judicious movement of parts in the baths and good bath agitation ensure even material removal, whatever the shape of the part. At all costs, hydrogen bubbles must not be trapped in the corners of the workpiece, and decomposition sludge must not settle on the workpiece, slowing down the etching process in places.