Here is Vacuum Casting Mold Factory talking about Precautions for alkali etching of cast aluminum parts.
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We all know that in addition to free silicon, cast aluminum parts also have a variety of compounds and other inclusions between the metals, and because of the loose structure of the cast aluminum parts, there may be a phenomenon of uneven chemical segregation, etc., while casting The unprocessed surface forms a dense oxide film upon post-cooling, which is a rough appearance of the cast aluminum part. Therefore, alkali etching is very important. If the alkali etching time is short, the cast aluminum parts may not be completely removed. If the time is too long, and the dissolution rate of the cast aluminum is faster due to alkali etching, the alkali corrosion tends to be caused by this. This causes over-corrosion of the cast aluminum parts, which causes variations in the tolerance dimensions and may even cause the product to be scrapped.
In view of the above situation, it can be solved by changing the alkali etching procedure, that is, alkali etching treatment after casting molding. According to the operation of the process, the occurrence of problems such as scrapping of the workpiece due to alkali corrosion can be prevented, and the surface quality after oxidation is favorable.
The above-mentioned alkali etching method can avoid the over-corrosion of the workpiece, and after the alkali etching, the 1:1 hydrochloric acid can be used for the rapid light-emitting of 2 to 3 s instead of the highly toxic hydrofluoric acid, which is beneficial to environmental protection and improving working conditions. It can also reduce production costs.