The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Can someone help me identify/solve this anodizing part flaw?

2004

1. The parts are a "drawn" aluminum .025" thick material 3003-0. The "drawn" part is approx. .75" deep.

2. The parts have been bright dipped ~ Bright Clear Anodized. The finishing spec. states the following: * Extended soap clean, * bright dip etch 1-5 min., * anodize .0001-.0003, *nickel acetate seal

3. The surface finish looks like it "lifted" to me.

4. Same old stories here, material supplier says it was the anodizer, anodizer says it is corrosion in the material. Anodizer also told us-the manufacturer of the AL blank maybe it was the oil we used when drawing the parts into the shape.

5. The "lifting" look or residue splotch is only on the top surface - it is not on the side of the parts.

6. Please see the pictures of the part, hope the pictures help because my description is not very good I am sure.

        

Thanks!

Michael Balda
- Prophetstown, Illinois, USA

---

First of two simultaneous responses --

Two thoughts come to mind.

#1. Corrosion/staining on the base metal, due to improper storage/handling, that was not removed in the anodizing pretreatment process (did you'all change lubricants, or the way you wash your parts prior to sending them out to be coated?).

#2.Bright dipping solutions can be difficult to rinse due to the viscosity. Its possible these parts weren't rinsed well prior to the anodizing step.

I noticed that the "stains" all run in a north/south direction (as pictured) which makes me lean towards it being a poor rinse prior to anodizing (typically, on large qnty jobs, all parts will be racked the same way). If it was a corrosion problem due to improper storage, or handling by the manufacturer, I would expect more of a "random" pattern to the stains.

Marc Green
anodizer - Boise, Idaho
2004

---

Second of two simultaneous responses --

You need to talk to a proprietary bright dip expert and I do not think we can list any directly on this forum. I think he will tell you that 3003 cannot be uniformly bright dipped or he may tell you that most bright dip research has been for 6061 and that probably some adjustment must be made to do the higher magnesium 3003.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2004

---

Robert brings up a valid point (although I'm not sure I totally agree, as 5000 series Al is high in Mg, and bright dips quite nicely), one question that should be asked, is this a first time job for you? Or, is this a new problem on an existing job where previously you've had no problems?

Marc Green
anodizer - Boise, Idaho
2004