Chromate treatment of aluminium

Can anybody help me with information on chromate treatment of aluminium.

I get some aluminium sheet chromate treated to improve the adhesion qualities. A thin film sheet is laminated to the aluminium.

Unfortunately with the last batch the adhesion was very poor, the laminated film came away easily.

Can anyone point me in the right direction to try to find a reason for this. Everyone involved with the process just shrugs their shoulders and say it can't be them.

I know nothing about treatments, I'm a designer.

Hi Richard,

If the chromate is coming off with the laminated substance, its your chromate shops fault, take the part back to them, beat them about the head and shoulders with it and have them re-do it for you (I was just kidding about that beating them thing).

Seriously though, if the film is powdery and or non-adherent it is a bad chromate and should be redone, no questions asked.