Formulation of a Long Life Etching Additive for Aluminium Etching Bath







Aluminium etching is a surface cleaning process for aluminium done before etching. Etching is done in tanks containing caustic soda to strip off the aluminium oxide and part of the base metal which build up as the tank is repeatedly used to etch more aluminium.


Chelating agents are used to chelate the dissolved aluminium thus prevent the precipitation. These include sodium glucconate, sorbitol and sodium heptanoate but they only work up to 50g/l of dissolved aluminium where the solution becomes excessively viscous and salts begin to precipitate.


Long life additives have been developed which combine sequestering properties of sodium glucconate and viscosity lowering agents to boost the lifespan of an etching bath. These baths can be operated up to 160g/l of dissolved aluminium where they stabilize with a low etching rate arising from the high aluminium in the bath coupled with the low bath capacity reduces the chemical consumption of the bath and increases the quality of the etched material. Phosphates were analysed using uv spectroscopy while sodium was analysed using flame photometry. Moisture content was analysed by evaporating in an oven at 105⁰C. It contained 57.41% moisture, 24.358 % sodium compounds. The rest of the remaining 18.232% was unaccounted for. This remainder may be some additional chelating agents such as sorbitol or sodium glucconate for which analysis was impossible. They may probably have also been some other additional components that increased performance of the additive hence the inconclusive analysis.


The etching additive was tested at intervals of 5,10, and 15 minutes.The weight losses were recorded as 13.8074 g without adding the etchant, 0.3621g with 5 minutes with etchant, 3.7240 g after 10 minutes with etchant and 15 minutes weight loss was 3.8876 g with etchant.

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