There are currently three types of etch used for anodizing aluminum: alkaline etching, mechanical etching and acid etching.
Out of the three the acid etch process uses chemicals to remove a layer of aluminum from extrusion or sheet, which changes the bright aluminum appearance to a dull matte finish.
It removes embedded impurities from the metal and smoothes out surface imperfections to produce a uniform surface. The result is a premium matte finish with low aluminum loss. Unlike alkaline etch, it also produces fluoride ions that attack the aluminum surface, producing a smooth grain edge.
Information source: Glass Magazine
Benefits of acid etch
Among many varying benefits of acid etching, one benefit is its ability to better meet the needs of extrusion, fabrication and reducing color variation. The acid etch process is environmentally friendly and accommodates for a higher percentage of recycled content in extrusion billet. It does not have any problems with water treatments and uses less water and has absolutely no cooling requirements.
Acid etching flooring is a fantastic way to bring out the life if your existing or new concrete floor. This process results in a smooth, sand textured surface that is also non slip.
Concrete that hasn’t been treated in any way after being poured can be too hard and smooth to accept paint or protective sealants. However, acid etching (or washing) concrete with acid opens the pores of the concrete and prepares the surface to accept its next treatment. Though it’s also possible to prepare the concrete manually by abrading it with a grinder, acid etching is generally much less labor-intensive.
Acid etching is most suited to outdoor areas such as driveways, patios and also wet areas like around your pool and outdoor spa.