Improvement for processes for continuous coating of metal surfaces with chromium metal and chromium oxide

摘要

The processes for coating metal surfaces with chromium metal and chromium oxide (Cr-CrOx) are improved by introducing a pretreatment consisting in at least one anodic pulse of brief duration applied to the metallic body to be coated immersed in the same chroming solution immediately prior to Cr-CrOx deposition.;In this way it is possible to perform this type of coating also on surfaces consisting of aluminium or alloys thereof, which has hitherto been impossible. Moreover the improvement ensures uniform adherent coatings which provide a firm anchor for subsequent painting. Finally there is a marked upgrading in resistance to corrosion, especially that of the cosmetic type.