BehrOxal~R - chrome-free coating for aluminum surfaces based on a newly developed spraying technology

摘要

A newly developed surface coating process has been introduced which improves the essential properties of A/C evaporators such as corrosion behavior, odor and water drainage. The activation of the aluminum surface occurs without the use of aggressive and toxic chemicals. For example, the yellow chromate layer grows on the oxide free aluminum surface only. Therefore, the natural oxide layer has to be removed in an etching step in an aggressive acid or alkaline bath with an additional rinse step. Even the precipitation of the yellow chromate layer, which occurs after the etching step, requires highly acidic conditions and toxic chemicals. The new surface coating is based on the activation of the aluminum surface by applying a high temperature. Due to the particularly high temperature the reaction rate of the protection layer generation increases rapidly. Furthermore, in order to develop an environmentally friendly surface treatment, the process management has been changed. Instead of dipping, a resource-intensive process step, the chemical solution is sprayed onto the aluminum surface. The Behroxal coated surface, which is covered by heavy metal free oxide layer shows clearly improved corrosion protection in SWAAT as well as reduced intrinsic odor and contact angle. The comparison of the two surface treatments has shown that the newly developed process has led to a marked reduction in fresh water and chemical consumption (over 95 %) because of the modified process management and makes a major contribution to improving ecological sustainability in the automotive industry.