Letter 15033

WHITE SPOTS ON T4 ANODISING [New Zealand] 

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WE HAVE BEEN ANODISING EXTRUDED T4 6261 HARD ALLY FOR AROUND A YEAR NOW. RECENTLY WE HAVE BEEN HAVING SOME PROBLEMS WITH THEM THOUGH. THESE ARE FRAMES FOR A CHAIR, AS SHOWN, IF THAT HELPS AT ALL. WE HAVE BEEN GETTING WHITE SPOTS AROUND DRAIN HOLES, AND A VERY STICKY SOLUTION AS WELL. HERE ARE THE FACTS ON THE MATERIAL USED.

T4 6261 HARD ALLOY, HEAT TREATED POST BENDING TO T6. 32 GRADE HYDRAULIC MINERAL OIL IS USED FOR BENDING AND WIPED CLEAN WITH TURPINTINE.

THESE ARE FIRST DEGREASED IN P3ALMECO, ETCHED IN A P3 ETCH, DEOXIDIZED IN P3 ALMECO 90, ANODISED IN SULPHURIC AND OXALIC ACID, AND SEALED IN ANOSEAL 30C. ALL CHEMICALS SUPPLIED BY HENKEL.

ANY COMMENTS OR QUESTIONS ARE MORE THAN WELCOMED.

ANDREW FALCONER
- CHRISTCHURCH, NEW ZEALAND

For the benefit of my clients I have just made a two page list of causes of "White Spots", and uploaded it into the Library section of finishing.com's web site. You mentioned the oxalate additive, well, Calcium Oxalate is a white powder. Get back to me, or any one else out there, with any other questions on "White Spots".

Robert H Probert Robert H Probert Technical Services Garner, NC, USA Editor's note:        Mr. Probert is the    author of Aluminum How-To

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