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


-----

Acid/caustic drippage onto anodized parts

I am writing to see if anyone has experience with drippage of acid/caustic from the anodizing racks on to the anodized metal. This is a major problem for us and results in reruns. If you have some info on this, I will appreciate it.

Everett Biddle
- Arkansas, USA
2003

---

Lots of experience on that. Remaining solutions even from the tiny crevices of the rack could spray out on the parts during blow drying. We usually correct this with longer rinsing time.

Further to this experience, the flight bars can also accumulate residue from the various chemical tanks. During the final stage of anodizing ie., hot sealing, steam could condense on the bar, dissolving the residue and drip on the parts.

Dado Macapagal
- Toronto, Ontario, Canada
2003

No where near enough information given. It is a fact of life that acid or caustic dripping on anodized parts can/will cause reruns. Now, what is dripping from where? Hand line or automatic? Big or little parts? This is only a start.

James Watts
- Navarre, Florida
2003

---

Everett,

This shouldn't be a problem with proper rinsing techniques. What type of racks are you using that would trap a lot of solution? You didn't go into too much detail, but the first thing I'd try would be to air-agitate your rinse tanks, keep that water moving around to flush out any trapped acids/bases. A good spray rinse never hurt anything either..I make it a point to spray rinse with DI water prior to the next process step as to avoid dragout/contamination into the next tank. Have you checked the pH of your rinse tanks to insure that IT is not the problem...perhaps the pH is too high, or too low? I seem to recall somewhere in the letters archives, a VERY informative article written on proper rinsing techniques (perhaps an article written by Ted?), take the time to do a search.

Marc Green
anodizer - Boise, Idaho
2003

----
Ed. note: Thanks, Marc. It's "20 Ways to Reduce Water Usage".

---

I ran anodize lines for 30 years. I have experienced the same problems. The key is to keep your flight bars clean. This can be done by having rinse tanks that completely cover the flight bars after etch and before the anodize tank. Numerable rinses in the right places will cure your problem.

Raymond Hendrix Troy, Tennessee
2003

We hose spray our DI water when our racks are in the air above the acid tank. This helps keep the concentration of our acid tank in place and at the same time eliminates the solution drag over. Hope this helps.

Jennifer Pinnel
Employee - Philadelphia, Pennsylvania
April 7, 2011