{"id":5224,"date":"2022-03-07T17:38:31","date_gmt":"2022-03-07T15:38:31","guid":{"rendered":"https:\/\/alufinish.de\/?p=5224"},"modified":"2022-03-07T17:38:48","modified_gmt":"2022-03-07T15:38:48","slug":"the-problem-with-zinc-in-acidic-aluminium-etching","status":"publish","type":"post","link":"https:\/\/alufinish.de\/en\/the-problem-with-zinc-in-acidic-aluminium-etching\/","title":{"rendered":"The problem with zinc in acidic aluminium etching"},"content":{"rendered":"

Particularly in the field of job coating, a certain proportion of hot-dip galvanised surfaces has to be treated in addition to a large proportion of aluminium surfaces.<\/p>\n

If only an acidic etching and degreaser is available for this in the plant, it becomes problematic. If both metals are pretreated in only one etching bath, both aluminium and zinc are brought into solution. Whenever aluminium surfaces are treated in a zinc-containing etching bath, zinc is deposited on its surface due to electrochemical processes. The higher the proportion of dissolved zinc, the darker and more visible the zinc-containing layer deposited on the aluminium surface usually becomes.<\/p>\n

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Dark discoloured aluminium surface after treatment in a zinc-containing, acidic etching<\/p>\n

If this problem were only an optical change of the surface, it could be concealed with the subsequent powder coating. Unfortunately, however, there is a much bigger problem. Zinc deposits lead to a massive deterioration of the corrosion properties on the painted aluminium goods. If these surfaces are subjected to an acetic acid salt spray test, the first visible signs of corrosion can appear after only about 100 hours.<\/p>\n\n\t\t\t\n\t