It is well known in anodising operations that, over time, deposits accumulate on the plastic balls used to cover (minimise heat and evaporation loss) hot sealing baths.
Unwanted white residue: a common problem that can be addressed
These usually show up as white, crust-like residues that are deposited and strengthened on the cover balls by ongoing drying processes. They typically consist of aluminium salts and tin(IV) compounds, depending on whether dyeing is used or not.
To avoid white run-off marks on the fabric, these cover balls must be cleaned or replaced from time to time. Alfikalk 7, for example, can be used for this purpose.
What causes black deposits on mechanically polished surfaces?
White or light-coloured deposits are known, but what is the cause when black residues suddenly become visible on the plastic balls?
The case in question concerned an anodising company that processes mechanically polished material in the pre-treatment process: cleaning – desmutting – anodising – hot sealing. During the inspection of the individual process steps, it was noticed that after the mildly alkaline cleaning, isolated black polishing paste residues remained on the goods – especially in corners and edges. These initially passed through the process steps of desmutting – anodising into the hot sealing bath without being affected. Due to the high operating temperatures prevailing there, the melting point of the remaining polishing paste residues was exceeded, and the paste residues dissolved in the bath. These detached, black residues were in turn picked up by the cover balls and finally led to the defect pattern described. Sealed goods that were subsequently removed from the bath then showed black run-off traces.
Gloss-retaining cleaning with Alficlean 154/4
The problem shows how important it is to clean mechanically polished surfaces well. Here, it is essential to find a cleaner that, in addition to the optimal removal of polishing pastes, at the same time only exerts a minimal etching rate on the surface. Otherwise, the polished surface will be clean, but the result will be a significantly lower gloss level. Therefore, you should use such a cleaning system that is suitable for pre-polished aluminium. Here, for example, the use of Alficlean 154/4 is a suitable option. In this way, clean surfaces are possible while retaining the degree of gloss.