Good, fast rust - Step by step process

Posted by Heath Satow on June 23, 19100 at 09:08:32:

In Reply to: Rust with muriatic acid? posted by Donald on June 07, 19100 at 21:21:52:

Actually, muriatic acid is best only for the initial etch. Every time you apply the muriatic, you'll just eat away any rust you've built up. The best method I've come up with is as follows:

*****Remember, always wear a respirator, gloves, goggles and proper clothing when using chemicals. It's best to work outside, too.*****

1) Clean steel with degreaser (like lacquer thinner or denatured alcohol)

2) Remove all millscale by soaking or spraying with muriatic acid, let sit until millscale rinses off. Repeat as necessary. If there is no millscale, rinse once with muriatic for a good etch. NOTE: You can replace this entire step with sandblasting if you have access to the equipment.

3) Make sure piece is completely rinsed with clean water.

4) Wet down entire piece with chlorine bleach, sprinkle lightly with salt, and allow to sit until it dries. Spray the piece with water, but lightly so the dried salt/bleach mixture doesn't rinse off. Just wet the surface down. Let sit overnight.

5) The next morning, mix up a pint of FRESH hydrogen peroxide (standard 3% stuff found at drug stores) with a tablespoon of muriatic acid. Spray this mixture onto the piece. Allow to dry. Once dry, spray once more with this mixture. Let sit overnight.

6) Next morning, rinse completely with clean water, and you should have a decent rust by now. If there are areas that need more rusting, go back to step 5. Once you are happy with this rust, let it sit for a few days, lightly wetting the surface with water whenever it completely dries out. This will help the rust to really "set in" so it's not just a light surface rust that will brush off.

7) Wet the piece with water one last time, sprinkle on baking soda to neutralize any acids left behind. Gently wipe the baking soda around on the piece, which should help clean off any rust that is too loose. Be gentle, though.

8) Allow piece to dry, wipe down again with paint thinner to clean of any superficial haze rust on top of the good rust.

9) Heat piece with torch, only enough to drive out any water in the metal. Do not over-heat. Only the get metal hot enough so you can still touch it for a second without burning yourself. (Maybe 200 or 300 degrees F)

10a) If you are planning on leaving this piece outside to continue to rust, you are done. But if that were the case, you could have stopped after step 3.

10b) If waxing the piece, do it immediately, while hot, to get wax to really get into the metal. Let cool completely before buffing out, then wax once more.

10c) If using a clear paint, let metal cool down to the point where you can comfortably leave your hand on the piece. In reality, avoid handling the piece as much as possible until painted. Paint as soon as possible. Once paint has fully cured, you may wax it if you desire.

Thatís it. Your results may vary depending on the environment, heat humidity, and the way you hold your mouth all affect the process, just like any patination process. I find warm weather with medium humidity to be the best conditions.     Good luck!  -Heath Satow   


From a discussion on "theforge" e-mail list
For nice pitting, sprinkle granulated salt, sodium chloride, on the hydrogen peroxide dampened surface. You can control the pitting by: how closely, how many and the size of the salt grains you apply.
I tried out the hydrogen peroxide method for the first time recently, and was astounded with what I got.
Here's the method I used:
It was a clear, warm day, and most of the surfaces were vertically oriented. I found that applying the HO with a spray bottle worked best. I used a newly opened bottle (for maximum strength) and did not water down the solution at all.
Here's the steps:
1) Clean metal completely. No oils or millscale can be on surface. The way I cleaned the metal was first a degreaser, then cleaning with muriatic acid. Sanding, sandblasting, or rigorous powered wire brushing could also be used.
2) Let the clean, dry piece warm up in the sun (I suppose you could lightly warm the piece with a torch or heat gun, but don't get it hot, just barely warm).
3) Spray on a coat of HO, just enough to wet the entire surface. I found this technique works best if the piece is warm enough to dry out in less than a minute. If any areas stay wet longer (like on horizantal surfaces where it can pool up), gently dab them with a clean rag or paper towel.
4) Repeat step #3 until you have the depth of coloration you desire. Make sure the piece is entirely dry before spraying more on. I found that after five or six rounds, I had a very deep beautiful redish brown color that was incredibly stable (didn't easily rub off). After that, the HO didn't seem to deepen the color noticably.
5) Seal surface with clear lacquer, oil, wax or whatever method you generally prefer. I also did a small test piece that I cleaned and wire brushed to a nice silver color, then gave two quick coats of HO, using the same process described in step #3 above. I then coated in with clear satin lacquer. It is a beautiful coppery red/brown color that still had a translucent quality, keeping the metallic qualities as opposed to a solid rusty coloration. I can't say
enough how taken I was with this finish. This is such a cool, easy, non-toxic finishing process that I plan to do a number of more experiments, varying the surface treatment prior to the HO application, (sanded, chemically etched, grinder marks, etc) and varying the application of the HO (sponge, rag, brush, soaked sawdust, etc) to see what happens.
Heath -Fusionworks ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
It is a fantastic way of getting different colorful rusts fast without the nasty chemicals. Peroxide works much faster if you add about a 1/4 cup of vinegar to the pint of peroxide and a couple of tablespoons of salt. If you heat the iron so that the solution almost boils off you get absolutely instant rust. You do have to put up with the vinegar smell. Sandblasting works great for cleaning the metal of oils, scale etc and gives the solution a nice surface to bite. Clyde Wynia 

Rust Finish for Steel

By Brad Silberberg, Bradley Metal Design, Inc.

Part 1 of 2

This finish will be a polished rust -- having the look of a old, well-used tool. It is an interior finish only, and if placed outside will continue to rust.

Surface preparation: First, sand blast the piece to be rusted to bare metal. Then, smooth the surface with a motorized wire brush wheel until shiny silver. (Brushing alone will not remove all of the black oxide from a forging.) Make sure that the wire brush wheel is not full of oil or grease from a previous work piece or it may get on the piece to be rusted and keep rust from forming. (New wire wheels are oiled at the factory.) Wear gloves to keep the oil from your hands off the piece as well.

Rusting solution: Mix up a solution of Ammonium Chloride (common name: Sal Ammoniac) and water, mixing about one teaspoon in one US gallon of water or a pinch in a coffee cup of water. This will form a dilute, buffered hydrochloric acid solution. While this solution is fairly weak, you should wear rubber gloves and eye protection and work in a well ventilated area.

Application: This is messy, so work on small objects in a deep sink, or set up a wood frame with a plastic tarp to make a containment for liquid run-off for large objects. Apply the solution by brush, sponge, or spray bottle to wet the entire surface of the object to be rusted. (For large objects, mix up this solution in a 2 gal. orchard sprayer.) The steel will start to turn yellow in minutes. Try to keep the liquid from pooling in recesses or on flat horizontal areas. Use a dry brush or a gentle blast of compressed air to remove the excess. (The pooled areas will sometimes not rust at all or turn black if the excess is not removed.) Wet the piece frequently with the sal ammoniac solution, rinsing with plain water once in a while between applications. You may need to turn the work over, on its side, or upside down from time to time to get all areas to rust evenly.

If large areas start to turn black, your solution may be too strong. (Experiment with how often to wet with water vs. chemical solution as well.) Edges and high spots sometimes turn black or do not seem to want to rust at all. Rub these areas lightly with a piece of Scotchbrite soaked in the chemical solution. They will usually end up looking like the rest of the piece.

The rate of rust growth is affected by temperature. If your shop is very cold in the winter, the rust will grow very slowly. The repeated evaporation of the rusting solution encourages rust formation and keeping the air around the work piece moving with a breeze from a fan will help. You can really speed up the rusting process by heating the steel before applying the chemical solution. Use a heat gun to get the piece hot-potato hot and mist with a hand sprayer. Shoot the mist above or across the object to be rusted and let it settle onto it. The solution will evaporate very quickly and needs to be repeatedly applied. (Take safety precautions from the fumes.) If the piece starts turning black it is reacting too vigorously and should be rinsed immediately.

Rust Finish for Steel

By Brad Silberberg, Bradley Metal Design, Inc.

Part 2 of 2

This finish will be a polished rust -- having the look of a old, well-used tool. It is an interior finish only, and if placed outside will continue to rust.

The following is Part two of a two part article.

Forging a rusty piece of steel makes the piece really hard to rust later. Even when it comes out of the forge oxidized black and has been sand blasted and brushed, some areas wonít want to rust at all, so clean rusty metal before forging. The alloy content of the steel will affect the rust rate and the color of the rust as well, with two identical looking pieces of different alloys turning very different colors. In general, if things are not turning out the way you want them to, start over by brushing on muriatic acid (used to clean mortar from masonry work) to etch off the rust. (This stuff is much more corrosive and protective gear and ventilation are imperative!)

Rust for one day for an orange rust with yellow in the low places, two days for more brown with orange tones. Do not rub the piece too much early on, as this newly formed rust is not very tightly held to the work. It will become more tenacious with time. You need to keep an eye on the rust as it grows. Walking away for long periods of time can result in odd streaks or unrusted areas. You can rust the work too much. It will become fuzzy and lose that polished look if you rust it more than two days so take care to get it started evenly.

You can experiment with different chemical solutions to achieve different rust colors. Using a solution of ferric chloride (available from Radio Shack as printed circuit board etchant) in water will give a different look. You can also try laundry bleach straight from the bottle or add between six drops to a dropper full of muriatic acid to a pint of 3% hydrogen peroxide from the drugstore. Substituting hot salt water after initiating rust with one of the chemical solutions will cause the rust to be more chocolate brown.

Neutralize: This will help keep your piece from becoming re-activated and rusting again later if located in a humid room. Neutralize the rust by rinsing the work a few times with baking soda or washing soda solution, about 3 teaspoons to a gallon of water.

Then rinse several times with very hot water. Allow the piece to dry thoroughly and wipe off the loose rust dust with a soft dry cloth.

Using sal ammoniac solution will turn any attached copper or brass greenish blue. You can leave this color or carefully buff it bright again with a wire wheel or Scotchbrite after rusting and neutralizing. Left colored or cleaned up, these metals contrast beautifully with the rusted steel. Adding gold leaf is also a very striking accent, but apply it before proceeding to finishing.

Finishing: Oiling with linseed oil-beeswax mix will produce an all-over mahogany brown. Lightly rubbing the high spots only, using a rag with partly dried-out oil/wax mix will leave orange and yellow in the low places, providing contrast. Waxing the piece with paste floor wax alone will yield a lighter orange-brown than the oil. Apply wax with the palms of your hands to keep it only on the high places or the lighter colors in the recesses will go dark too. When the wax is buffed up, the rust finish will look almost like polished wood.