Additional information: Rinsing of PCBs
Electrolytic and chemical polishing processes for aluminium
Industrial electrolytic and chemical polishing processes for aluminium are of two types:
- Processes designed to replace or reduce mechanical polishing. These provide a smooth, bright, though not a “mirror”, finish, and are characterised by high dissolution rated (between 2,5 and 5,0 μm per minute). In most cases, the best results are obtained on high purity aluminium or its alloys, but some processes may be employed on commercial purity based grades of aluminium, producing a correspondingly lower grade of finish.
- Processes employed after mechanical polishing. These processes have a low rat of attack and are employed on aluminium reflectors and other components which require a higher specular reflectivity than is obtained by mechanical methods alone. Their use is generally restricted to high purity based materials as reflectivity falls off sharply as the quantity of second-phase constituents present increases.
Hot, highly concentrated acid mixtures are normally used especially phosphoric acid, sulphuric acid and sometimes nitric acid. The temperature is >80°C.
Source: BAT Surface Treatment of Metals and Plastic, Aug. 2006.