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


-----

Aircraft firewall cleanup

January 9, 2010

I own an aircraft that has the engine of off it for overhaul and the motor mounts are off for inspection and powder coat. This leaves a fully exposed zinc coated steel sheet firewall. While the oil and dirt that are on the firewall are easily taken care of, the surface is rough to the touch and just looks dirty. Since the purpose of the firewall is to keep fire from entering the cabin and zinc helps to keep the steel from rusting (I assume, I am not a metallurgist), is there anything, or process, that I can do to help clean this up and make it look better. I assume the zinc is a coating and not mixed in with the steel. Abrasives would help of course, but I am worried about removing the zinc and ruining the integrity of the firewall. Are there chemicals (with safe handling) that could be used? Are there coatings available that could be applied that do not require baking (the firewall cannot be removed, at least $$ wise, it can't), would look great and maybe come in colors and be fire, oil and solvent proof?

Any answers are greatly appreciated. Thank you in advance.

Rick Stottle
hobbyist - Dallas, Texas

---

First of two simultaneous responses --

Try WD-40 [on eBay or Amazon] or Balistol, or if you prefer D-I-Y solutions you can use 1 lit petroleum/20 gm parafin (small piece of candle) solution. Zinc can be cleaned with 5% sulfuric acid,after treatment neutralize with baking soda [on eBay or Amazon] solution and then rinse well with water.Try special aluminum powder based paint (it can stand up to 400 °C heat) -- I think you can make your own-simply mix aluminum powder with 20% shellac.Hope it helps and good luck!

Goran Budija
- Zagreb,Croatia
January 14, 2010

---

Second of two simultaneous responses -- January 14, 2010

Sir:

I would leave it alone. If you are compelled to make it look better, then use suitable primer and paint (perhaps after light cleaning). There is always the possibility that paint will peel off of galvanizing.

There is a galvanizer who specializes in painting after galvanizing and his process is called COLORGALV. Likely you can find it on the internet. I think he only deals with freshly galvanized surfaces.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA

---

January 14, 2010

Sir:

5% sulfuric acid is much too strong to put on galvanized product. Try a weak acetic acid [on eBay or Amazon] solution (e.g. distilled vinegar [in bulk on eBay or Amazon]).

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA