Acid Etch vs Caustic Etch

Can Art is pleased to announce the addition of Acid Etch technology to its new anodizing facility. Acid Etch is an alternative to traditional caustic etch; providing a superior cosmetic appearance to clear and colored anodized product and more consistent finishes for repeat orders. In addition significant environmental benefits are also achieved.

Etching is a process that takes place in the pretreatment segment of an anodizing line. During pretreatment, grease, oil, dirt, and other contaminants are removed from the aluminum to provide a clean surface to use for the formation of aluminum oxide in the anodizing tank. To provide a premium visual appearance, etching is performed to minimize or eliminate surface defects such as shadow lines, flow lines, die lines, and light surface scratches. Conventional anodizing lines etch away aluminum using caustic soda, an aggressive alkaline chemical, in an attempt to mask some of these surface defects. Acid etch uses fluoride based ions that attack the microstructure of the aluminum, resulting in a significant reduction or elimination of most surface defects while providing a premier matte finish.

With conventional caustic etching, upwards of 10gm/ sq.ft. of aluminum is etched away from the surface of the aluminum. This is a process that typically lasts 12-14 minutes for each part being anodized. With Acid Etch technology, only 1gm/sq.ft. is removed from the surface of the aluminum, cutting etching times by up to 80%. This process leads to a more consistent matte finish across every order.

Acid Etch provides an environmentally friendly approach to anodizing. During etching, the aluminum that is removed from the surface of the extrusion gets converted to a sludge that becomes landfill waste.  By removing 90 percent less aluminum from the surface of each extrusion when compared to caustic etch, proportionally less landfill waste is produced during the process. The reduction in etching time during Acid Etch also results in lower energy consumption. Lastly, anodizers and end users have traditionally had problems duplicating the quality of the anodized finish on products derived from recycled aluminum when compared to products made from primary aluminum.  With the increased ability to hide surface defects, Acid Etch allows for more secondary LEED compliant billet to be utilized in today’s greener marketplace, without having to compromise on surface finish quality.