The authoritative public forum
  for Metal Finishing since 1989
-----

Smut in seal after anodizing and electrolytic coloring again!

Hi there,

We are experiencing heavy smut on our colored finish.
We are using ammonium acetate for our sealing additive and maintained the pH of our bath to 5.6-5.7.
We used Tin sulphate electrolytic coloring and 6000 series type of alloy.

Any suggestion regarding this matter? Thanks.

Eugenie H. Gateb
aluminum company - Cainta, Rizal, Philippines
2006

---

2006

Hi Gene,

In Hot Seal the smutting is expected to some extent and it becomes pronounced especially when the bath is old. However this obviously indicates that the sealing is complete. Now-a-days every Anodiser uses a ready mix seal additive suitable to their water quality in seal bath to inhibit the formation of smut. You should contact your chemical supplier for this additive, or else you have to maintain the bath conductivity not higher than 60 microS. And this certainly will be expensive operation as the other one which requires manual cleaning of the surface with metal polisher.

Good luck
Basu

Srimay Basu
Dubai Aluminium Co. - Dubai, U.A.E.

---

Hi Basu,
We are experiencing smut even when our sealing is new. We are using ammonium acetate as our sealing additive and DI water for our hot sealing. At the middle of the week, we are doing partial dumping to reduce the contaminant of the bath. We are sealing our profile 2 mins. per microns and try to reduce the sealing time till it fails sealing test. Any recommendation regarding this matter. Thanks.

Eugenie H. Gateb
aluminum company - Cainta, Rizal, Philippines
2006

---

Hi,
I was busy all these days - didn't see your later question, sorry.
Now you may have to give us detail about your product, especially the product type & the alloy, you are using.
Sometimes it may happen that due to some metallurgical flaws this problem may encounter - wait till your reply comes.

Basu

Srimay Basu
Dubai Aluminium Co. - Dubai, U.A.E.
June 3, 2011