Aluminium immersion etch

In this procedure the first step, once again, is to pickle the aluminium substrates in accordance with the specifications quoted above. Under certain circumstances it may be sufficient to use only an alkaline degrease before anodising. The etched panels are then clamped to the anode of a standard anodising bath and are immersed in a solution of phosphoric acid at 25°C. Anodising then takes place in accordance with one or other of several European and American specifications [29,30]. A typical bath composition is ... 

In many cases, the chemically pretreated substrates will require desmutting after etching and washing. This can be accomplished by immersion in the standard CSA pickling solution (see above) for 5-20 min at 60-65°C. Once such a bath has been used for desmutting stainless steel the pickle cannot be used again for the pretreatment of aluminium. 

After the machining and the deburring, the die cast part is cleaned by using an alkaline solution. In some cases, there can be an etching or pickling step applied before the conversion treatment. The conversion coating can be applied, for example, for aluminium by immersion into a bath or by spraying. 

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