Where the
world gathers for metal finishing
Q&As since 1989


-----

Titanium Rack for aluminum anodizing turned pink

April 23, 2009

Greetings,

We have been anodizing aluminum (7075, 6061, and A380) for two years. The parts have been loaded on the same titanium racks for the life of the process. Today, one of the titanium racks turned pink. A quick dye check indicated that the aluminum parts were anodized, but we are quite puzzled about the pink rack. Does anyone know what happened?

Thanks

Michael Costello
plating engineer - Grand Junction, Colorado, USA

---

First of three simultaneous responses --

A wild guess. The operator left the material in the anodize tank with the power off for a period (for some reason) and the dissolved copper immersion plated the rack. Is your anodize tank a light to mid blue color?

James Watts
- Navarre, Florida
April 27, 2009

---

Second of three simultaneous responses --

Titanium "anodizes" to a different color as a function of current, and voltage. Pink is normal, does not hurt a thing. Not to worry.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

April 27, 2009

---

Third of three simultaneous responses --

Michael,

The colour you impart to your jigging during anodising is due to how the coating absorbs and reflects various light waves. When you anodise you put a very thin oxide layer on the surface and this can appear to be many colours, including pink, but it can also appear to be yellow, green, blue, purple and grey. You haven't done anything wrong, it is just the nature of the process.

Brian Terry
Aerospace - Yeovil, Somerset, UK
April 28, 2009

I have personally never seen a pink rack with sulfuric anodizing from 13 to 19 volts and 68 -70 F.

James Watts
- Navarre, Florida
April 30, 2009

I've seen pretty much every colour under the sun. Pink is more associated with chromic acid anodising, but I have seen pink from sulfuric.

Brian Terry
Aerospace - Yeovil, Somerset, UK
May 5, 2009

---

May 8, 2009

Hi

Titanium Rack becoming colored is a common scenario. You can remove the oxidation by immersing the rack in the sulfuric acid anodizing electrolyte say for about 10 -12 Hours (over night).

regards

Keshava Prasad M
- Chennai, India