Acid etch is the new standard in achieving a matte satin finish on architectural extrusion before anodizing over traditional alkaline (or caustic) etching. Acid etching is superior in hiding die lines, fine scratches and other surface defects on extrusions in achieving a consistent matte satin finish that is difficult to attainable with alkaline etching. Furthermore, both alkaline and acid etch works by dissolving a thin layer of the aluminum. But acid etch achieves a better result while dissolving only about a tenth of the aluminum dissolved by the alkaline etch.
Acid etch can also be used to achieve a finish similar to glass beading on non-precision machined parts and sheet metal parts. However, since acid etching involves the chemical removal of some material from all surfaces of the part being etched, it is not suitable for high precision parts.