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Zinc castings require vapour blasting before Alochroming

I currently work on a product which has a Zinc casting which requires reasonable good quality appearance after finishing even though it eventually ends up hidden from view. To this end it is Alochomed as per our aluminium parts. We have experienced quality issues however with the finish of the Alochome over the casting and would welcome any advice on pre-treatments to improve this. We have just tried Vapour Blasting which certainly seems to do the trick but other comments would be appreciated.

Paul Sayer
Aerospace Displays - Broadstairs, Kent, England
2003

While it is theoretically possible to apply chromate conversion coatings directly on zinc die castings, it seems that most people find that the results are unsatisfactory just as you did. An alternative to vapour blasting would be to zinc plate the castings before chromating.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

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