I've had this Maine 'buoy bell' wind chime for about eight years now. I really like it. It has the haunting melancholy sound of a bell buoy at sea being tossed by wind and waves. It is made of COR-TEN steel which is designed to rust on the surface to create a protective barrier against further rusting. It came painted black on the outside and was supposed to develop this rich rust patina naturally over time. Well, the unpainted inside did rust completely after about a year, but the outside only rusted slightly, near the bottom, even after exposure to the sun, rain, and snow of the northeast for eight years. I wanted it to have a nice rust patina that looked like it had been hanging on the eaves of a lobster shack, at the end of a pier, for many a year, being splashed and buffeted by nor'easters and sudden gales. Seeing it was taking so long, I decided to take things into my own hands and, ah, "help" mother nature along and accelerate the process. I searched the net and found mostly dangerous methods to induce rust on steel using highly caustic or acidic chemical solutions. However I finally did find a simple safe method, using on-hand household chemicals, buried deep within a thread on the subject at a metalworking forum. I got spectacular results which have not only withstood the wind and rain of the southwest but have actually improved with the help of mother nature. I like the results so much, and there is so little practical information on the subject that is accessible to the general public, I thought I'd share this simple method with the instructables community.
Judging by the number of posts on forums asking how to do this, I see I am not the only one who wants to actually promote, rather than prevent, rust on iron and steel objects. I found out the basic information for doing this at the very cool ArtMetal forum: http://www.artmetal.com/blog/bob_turan/2009/04/rust_promoter . I'm guessing that there are more than a few instructables members who have a similar desire to prematurely age some iron/steel artifact, so I encourage people to post pictures of their resuls in the comments and add tips on how they did it so we can all learn. This method is not set in stone. Posts about useful variations on the method are always welcome.
Step 1: Materials and Tools
You will need the following:
- White vinegar (any brand)
- Hydrogen Peroxide (3% -- use a fresh bottle)
- Table salt (any kind will do, doesn't have to be sea salt)
- Degreaser (any brand)
- Measuring cup
- Measuring spoons
- Spray bottle
Step 2: Safety First
You will need the following safety items:
- Safety goggles (enclosed type for chemicals not open type)
- Chemical resistant gloves (available at home stores)
You will be using an acid, vinegar, and an oxidizer, hydrogen peroxide, so do wear the safety goggles and gloves. Be careful where you spray the solution. It is mildly corrosive and will rust anything made of iron or steel. Do this outdoors preferably in a place sheltered from the wind and away from people or pets. Do use common sense and follow common safety practices. Do not spray chemicals at anything other than the object you are trying to rust. Obviously don't spray it anywhere near people or animals. Don't breathe the vapors. They are irritating. Don't get it near your eyes or anyone else's. If you do get some in your eyes, go and rinse your eyes with cold or lukewarm water immediately. Although the chemicals used are relatively safe, common sense should prevail. If you do not possess common sense, please don't try this at home, or anywhere else for that matter.
Now that we got that out of the way let's get started.
Step 3: Degrease the Metal
I am assuming you already have a clean iron/steel object that is free of any paint or other protective coating. If not you need to strip the finish first before performing this step. I won't go into detail about how to do that since that information is readily available. Read the label on the container of paint stripper if you use that. I used paint stripper to remove the sun-baked paint from my bell. I had to give it a second treatment to remove all traces of paint. I used a paint scraper to remove most of the paint but the paint around the rust spots required the use of an abrasive pad, wetted with the paint stripper, and a lot of elbow grease. Obviously wear goggles and gloves to do this. Nasty stuff.
Once you have clean metal you need to degrease it so chemicals will penetrate the surface. Again wearing goggles and gloves, apply degreaser according to instructions on the bottle. Be sure to remove all dirt and grime as well as oils from the metal. Rinse it well to remove all traces of degreaser. Rinse your gloves well before handling the degreased metal. You don't want to add back any dirt or oil. Don't touch the metal with bare hands or you will make oily fingerprints which might show up on the final finish. Now take your objet d'art to the outdoor place where you will spray it with chemicals.
Picture below shows clean degreased metal ready for the next step.
Step 4: Pickle the Metal
This step is critical so don't skip it unless you actually want non-uniform rusting. At first I didn't do this and several areas would not rust because the solution could not penetrate the surface of the metal. You can see this in the picture below. I simply hung up the degreased bell and sprayed it with solution. You can see where the solution did not penetrate. Those areas did not rust at all. I then pickled the entire bell and after I did it rusted all over.
Believe it or not, you can pickle metal with the same ingredient that is used to pickle cucumbers. Yup, you guessed it, vinegar. Place your object where you can spray it from all sides, away from anything you don't want to get sprayed, including people, pets, and other objects. Put on your safety goggles and gloves. Put some vinegar in the spray bottle. Not too much, just enough to cover the object several times. Spray the object from top to bottom all around. Soak it good. Let dry and repeat several times. The more the better. Placing the object in direct sunlight will speed drying. The acid in the vinegar will etch the surface of the metal so chemicals can penetrate. If you skip this step and proceed with the next step or don't like the results of the next step, just come back to this step and spray again with vinegar. The acid in the vinegar will dissolve most of the rust. Don't worry about it. This is normal.
That's it. Now we're ready for the fun part.
Step 5: Rust the Metal
Now for the step you just can't wait to do. This is the exciting part.
Wearing your safety goggles and gloves, mix up a batch of rust accelerator adding ingredients in the order given:
- 16 oz Hydrogen Peroxide (use a fresh bottle)
- 2 oz White vinegar
- 1/2 Tbsp Salt
I assume you have placed your awaiting object in a safe place away from people, pets, and things you don't want to get rusted and by now you are dying to see some rust. Are you ready? OK. Let's go.
Spray some solution onto your object, soaking it from top to bottom all around. Now sit back and watch the magical transformation. It will start foaming and begin to rust before your eyes. Is that something or what? If it doesn't rust then you didn't degrease it enough or you didn't pickle it enough and will have to repeat one or both of those steps. Another possibility is the temperature is too cold. This works best at elevated temperatures. It is best to let the object sit in direct sunlight and heat up a little. Let it dry and repeat. I only had to let it dry for 5 minutes but YMMV (Your mileage may vary) depending on the ambient temperature. The rust patina should deepen each time you repeat the spraying and drying cycle up to a point beyond which there is no noticeable change. Keep spraying and drying until you are satisfied with the degree of rusting. I repeated the cycle about 6 or 7 times but again, YMMV. The pictures show the progression of the rusting process.
Congratulations! You have greatly accelerated a natural process and now have a piece of metal with an attractive aged-looking patina.
Step 6: Finishing Up
I would advise you to dump the remaining accelerator solution from the spray bottle and rinse the bottle and spray head well with clean water. Then spray some water through the head. This will help prevent the spring inside from rusting. You can save the solution in a jar with a plastic, not metal, top if you like, or just dump it in the toilet, flushing immediately, or in the sink, flushing it down the drain with lots of water.
Now you have several options. Be careful not to touch the surface of the rust. It is very delicate right now and powdery and can come off by rubbing. Not all of it but enough of it. You can go hang it like I did and let mother nature take over. The last picture shows the bell after a torrential downpour and subsequent drying by the sun. You can see that the color deepened from an orange color to a deeper brown color. The grain is also coarser. Or you can spray it with a fixative like acrylic or polyurethane spray. Some people recommend rubbing it with salad oil. I wouldn't, because, first, it would be messy, and second, salad oil will become gummy after a while. Mineral oil would be preferable but still messy.
And that's it. Wasn't that easy? One note. As I mentioned, my bell is made of COR-TEN steel, which is designed to rust on the surface to prevent any further rusting. Other steels are probably different in the speed at which they rust and may require more or fewer spray/dry cycles. I hope people will report their experiences in the comments section. Now that you know how it's done, go and rust something and tell us all how it came out. Have fun.