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Acid washing aluminum, Primer Application over Anodize

Q. I am involved with an aluminum finishing process of chromic acid anodize which incorporates a nickel acetate seal. Afterwards, the parts are handled in several other operations, and the freshly anodized parts become contaminated with lubricants. The surfaces are wiped down several times with IPA after each operation. In the paint shop, the parts are wiped down again before a wash primer is applied. After drying, the parts are topcoated with polyurethane.

I have experienced numerous adhesion problems with test samples which are painted right out of anodize. The 24hrs. immersion, wet tape test is performed. The samples are wiped down with solvent prior to painting, but not to the extent that the actual parts are in production. When the parts are tested with the wet patch method, they perform very well. I am concerned that the application of the wash primer over the nickel acetate seal is not a very good idea. Do you have any thoughts on this subject ?

Ed D [last name deleted for privacy by Editor]
- Columbus, Georgia, USA
2003

A. Do not seal the chromic anodize and the paint will stick better.

Certainly do not seal with Nickel Acetate (some school boy engineer got all mixed up).

Better still, do not solvent wipe, thus letting solvent get into the anodize film, unless the solvent is the same one used in the paint.

Wash Primer is for bare metal. Wash Primer should not be used over chromate or chromic acid anodize. There is an engineer at Lockheed in Syracuse that wrongly specifies acid wash primers over chromate. If you anodize do not wash prime.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003

Need acid wash before anodizing in lieu of bead blast

May 12, 2009

RFQ: Looking for a source prefer in the southeast to:
1) Acid wash to eliminate bead blast on aluminum and stainless steels.
or
2) A dealer to discuss set up of process.

Kevin W [last name deleted for privacy by Editor]
mfg sales rep - Hartselle, Alabama, USA

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

"The Surface
Treatment &
Finishing of
Aluminium and
Its Alloys"
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Acid wash after anodizing

Q. Hi,

I saw some metal sheet used on the EMP museum in Seattle Washington. I was told they used a process of anodizing polishing and acid wash -- but in which order I don't know, and to what extent I don't know. Can anyone tell me about this process? It made a very nice looking finish. One was a bluish and the other was a reddish.

Thanx,

Paul I [last name deleted for privacy by Editor]
- Salem, Oregon, USA
2003

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