Metal finishing Q&As since 1989

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Steel furniture components are till rusting after tool-black surface

March 27, 2009

Hello,
I am a sculptor accustomed to working in bronze but lately have been with a studio that is doing a lot with tool-blacking process on cold-rolled steel. I believe that the composition is 5150, but, again I am a bronze woman and my steel knowledge is pretty limited. We are using two different industrial products as the chemical reactor, first cleaning with a mix of dry wipe, denatured alcohol and then applying the tool black, allowing it to sit and finishing with a water rinse, wipe and wax sealant. The issue is that after a few hours to a day, rust is coming though the wax removable by the touch. When I strip the wax down with sawdust and water it seems better for a day or so, but I think the exposure to air is making it rust again. The studio I am working for now, make mostly fine wooden furniture and we are including steel components into the designs now. It is very important that there is no iron based material coming though because of the direct placement next to the wood (mainly walnut) that I am afraid the oxides will activate the wood tannins and cause corruption. I have heard from a colleague that a mixture of baking soda [on eBay or Amazon] and water or baking soda and denature alcohol will work to seal or "freeze" the chemical reaction and then covered with wax to seal the steel. Does anyone have any suggestions or knowledge in this area? We are hoping to do the process as cheaply, efficiently as possible. We don't have a lot of metal working tools, the shop is primarily wood based, so that is an obstacle. Thanks!

Meg Bye
Woodworker/ sculptor - Chicago, Illinois

If tool black is some sort of rust converter [on eBay or Amazon] or anti rust coating you must clearcoat it -probably good primer and 2 topcoats may be option too. Hammerite Rust Cap [affil links] paints are very good and you can use them on slightly rusted metal.Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia
March 31, 2009

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Hummmm. If the stuff you are using to blacken the steel with is an acid type you will have the problem that you are describing forever. I have never found an acid blackening solution that worked wel. As a Gunsmith I have been mating blackened steel to French, English, Black, Brazilian, Peruvian, Claro and Circassian walnut for 25 years. Also maple, beech and myrtle wood. Some of these woods are very blond. We hot caustic bluing salts to color steel parts which is in truth closer to black. These parts never seem to stain the wood and special gun oils, paste wax or spray on lacquer can be used to keep the blued parts from rusting. I have seen guns over 100 years old with metal parts blackened in this way that show no damage to the wood that the parts touch. Also caustic blacking does not rub off on your hands like acid blackening. Some plating shops and machine shops offer this service. Almost all custom gunmakers and gunsmiths do as well. I can't speak for the platers or machine shops but most gunsmiths will charge you $25 to $50 to blue about a gallon of small parts or 2 to 4 larger pieces providing all the metal preparation is done for them. (Removing all rust, paint etc. and polishing the parts to bare metal). Caustic blacking unlike acid blacking never rusts as long as it is protected. For some reason it seams like you can never remove all of the chemicals from acid blackened parts and they continue to work a bit even after it is oiled or waxed. I can't say why I'm not a chemist but I have worked with acids and they sucketh royally! As gunmakers and gunsmiths hot caustic bluing or blackening has been working fine for us the last couple hundred years so there must be something to it. Get out the yellow pages and call a few places and see what they charge. Rod

Rod Henrickson
gunsmith - Edmonton, Alberta, Canada
April 1, 2009