The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Failure of Hardcoat Film

1999

Dear sir,   We received a project for producing a hardcoat product.  The hardcoat sample we prodcued can not passed the direct flame heat test.  The color fades away from a very desirable deep grey color shade after a 3 mins. direct flame burning condition (This is required by the customer).  No visible cracks are observed on the surface.  Our working conditions are :-   Acid content : 16%, Temperature : 9C, Voltage : 20V, Thickness : 38 um, Al content : 15g/l, rectifier type : conventional non-pulse type, Shade : deep grey.   and also :-   Acid content : 16%, Temperature : 13 C and 22 C, Voltage : 22V, Thickness : 38 um, Al content : 15g/l, rectifier : pulse type, Shade : deep grey.   Both condition did not work because of the color fading.  We could not possible figure out why nor our folks here working for the hardcoat area.   We really appreciate if you can have some hints for us becuase we are about to lose this project.   Many thanks in advance.  

syyuen

---

Your process conditions are more appropriate to a thick commercial anodize than to a hardcoat. For a true 38 µm hardcoat, used a stepped voltage or current control to a terminal voltage of 45 to 50 volts. The precise value depends on a number of processing parameters, including the aluminum alloy. The bath should be chilled to 0C with Al content below 12g/l. This will result in a harder, denser, and more temperature resistant coating.

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.

Wadsworth, Ohio

1999