You can use several methods to color a metal surface. The choice depends on the metal alloy of which it is composed and on the result you intend to obtain. You can make an item look like new by giving it a fresh coat of paint, create an antique patina or change color with the anodizing process. What determines the value of an object is its finish, so choose a method that suits the needs of your work.
Steps
Method 1 of 4: Paint with Spray Paint
Step 1. Eliminate mold
Start by soaking the item in bleach to remove mold and discolouration. Make a solution by combining 3 parts of water and 1 part of bleach. Let it soak for about 20 minutes. Then rinse it off with clean water. If the metal is new or has no mold, you can proceed without soaking it in bleach.
Step 2. Remove the rust
Scrub the surface with a wire brush. To remove all traces, you can also use an electric sander with a coarse grit disc, an electric drill or a rotary tool. Choose a sandpaper between 36 and 100 to eliminate rust and sand any imperfections.
- Wear eye protection and a dust mask to prevent metal fragments from getting into your eyes or lungs. Use a pair of work gloves to avoid the risk of injury.
- If you need to treat a large object, you can remove rust, debris and old paint with a liquid rust remover.
Step 3. Clean the item with white spirit
It is a paint thinner that does not contain turpentine. Clean the metal surface with a rag dipped in white spirit. Remove dust and residue from sanding. For the primer to adhere, make sure the object is completely clean and dry.
- Keep in mind that white spirit removes any traces of fresh paint.
- Also, remember that it can only remove fresh paint. If you want to remove the old one that doesn't come off with white spirit, try cleaning the metal with turpentine.
Step 4. Apply primer
Spray it on the surface to create an even and homogeneous layer. You should pre-treat the item with this product immediately after cleaning the surface to prevent dust or rust from accumulating again. Choose a primer specially formulated for the metal you are coloring.
- If you can, buy a spray of the same color as the finish.
- Try purchasing a primer from the same brand as the paint, as the colors are more likely to be similar and chemically compatible.
- Purchase a rust resistant primer.
- It is very difficult to apply the primer with a brush without leaving streaks. Use a spray for best results.
- Read the product instructions to find out how long you need to wait for it to dry.
Step 5. Apply an even coat of paint
Make sure you shake the can first. Press and hold the nozzle and color the areas you want. Use masking tape to cover the spots you don't intend to paint. Keep the can about 30 cm away from the object. Start spraying sideways and move the spray across the surface without stopping. Let the first layer dry.
- Examine your surroundings. If you need to paint a small object, you can put it in a cardboard box and apply the paint.
- If you stop dispensing, a stain may form. Immediately use a cloth to wipe off any fresh paint before it dries. Let the rest of the paint dry before starting over.
- Galvanized metal has a thin layer of chromed zinc. The reason paint flakes or does not adhere to this type of material is that it binds to the zinc coating or residue accumulated on the surface, rather than the metal. In this case, get a product that does not contain alkyd resins, otherwise the oil-based substances of which it is composed may react with the zinc coating.
Step 6. Apply a second coat of paint
Once the first coat is dry, apply another one. This way, the paint will last longer. Then wait for it to dry.
For best results, always wait 24 hours between applications
Method 2 of 4: Anodize the Metal
Step 1. Learn about the anodizing process
The anodization forms a protective oxide layer on the metal surfaces. Anodized aluminum oxide is unalterable and incredibly resistant to corrosion. Furthermore, it is more porous than non-anodized aluminum and allows the absorption of many metal pigments.
- The anodizing process requires the use of electric current and the immersion of the metal in a strong acid. The metal to be anodized is connected to a circuit and immersed in the acid, which acts as an anode (positive electrode). The negative hydroxide ions present in the aqueous solution are attracted to the positive anode and react with the aluminum to form aluminum oxide.
- A piece of aluminum is also introduced into the acid solution, connected to the other wire. It acts as a cathode (negative electrode), closing the circuit.
- Aluminum is the metal mainly used for this process, but other non-ferrous metals can also be anodized, such as magnesium and titanium.
Step 2. Collect the supplies
Start by finding a space in which to work without causing damage. You can procure the following tools individually or purchase a metal anodizing kit that includes everything you need.
- Choose the metal. You can anodize aluminum or any aluminum based alloy. Other types of metal, such as steel, are not good.
- You will need three plastic containers. Each should be large enough to hold the object to be anodized. One will be used for the cleaning process, another for acid and the last for the dye bath. Plastic paint buckets will work for these tasks.
- For the neutralizing solution, get a plastic jug.
- As reagents, you can use sulfuric acid, baking soda, caustic soda, dye for metal fibers and distilled water.
- Find a suitable power source. You must have a power supply capable of producing a direct current of at least 20 volts. A car battery is ideal.
- Get two electric cables to connect the car battery to the acid solution. They should be sturdy enough to grab onto the metal object and lift it or insert it into the solution.
- You also need to equip yourself with another piece of aluminum to act as a cathode within the solution.
- Get a large saucepan and stove to heat the metal object.
- Always wear a pair of oversized rubber gloves. Since you will have to handle harsh chemicals, pay attention to your safety by preventing them from coming into contact with your skin.
Step 3. Prepare a neutralizing solution
It is composed of sodium bicarbonate which acts as an alkaline agent capable of neutralizing the pH of sulfuric acid. You must keep it handy to clean equipment and cancel the action of sulfuric acid in an emergency. If the skin comes into contact with acid, use it to relieve the burn instead of using water, which could aggravate the condition of the wound.
Pour 360g of baking soda into 3.8L of distilled water
Step 4. Prepare the metal
With this procedure you can anodize any aluminum alloy. Put on a pair of rubber gloves before cleaning the item. All traces on the surface, even those of fingerprints, can affect the results.
- Wash the metal with water and dish soap.
- Put it in a solution of water and caustic soda. Pour 420 g of caustic soda for every 3.8 liters of water. Use a pair of rubber gloves, soak the object in the solution for about 3 minutes.
- Rinse it with distilled water. If no droplets form on the surface, the aluminum is clean.
Step 5. Prepare the sulfuric acid solution
Pour the sulfuric acid into a plastic container containing distilled water. The ratio must be 5 to 1 respectively.
- Do not use a fragile container, such as glass.
- Always add acid to the water so that the solution does not foam. On the contrary, it could leak out of the container.
Step 6. Prepare the power source with positive and negative poles
Before activating it, connect one wire to the positive and the other to the negative.
- Connect the other end of the negative cable to the metal object and immerse the object in the container containing the sulfuric acid solution.
- Connect the other end of the positive lead to the piece of aluminum and dip the piece of aluminum into the solution without touching the metal object.
- Turn on the power source. The voltage to use depends on the surface of the metal you want to anodize. Check the power supply. Start with a low voltage, around 2 amps, and after a few minutes increase it to 10-12 amps.
- Anodize the aluminum for 60 minutes. Negatively charged aluminum will attract positively charged sulfuric acid. You will notice a large amount of bubbles forming around the piece of aluminum, but few around the object to be anodized.
Step 7. Remove the metal piece and wash it thoroughly under running water
Be careful not to drip the acid. Keep the container containing the neutralizing solution under the metal as you move it to the sink. Put it under running water for a few minutes and turn it over to clean it on each side.
Step 8. Prepare the tincture
In a separate bowl, prepare a solution of fiber dye and distilled water to get the color you want. Follow all the instructions of the product you have purchased.
Step 9. Immerse the metal object in the dye bath for a maximum of 20 minutes
You will probably only have to leave it on for a minute or two, depending on the shade you want to achieve. You can also slightly heat the solution to speed up the process. At first you will have some difficulty getting the color you want, so try several different pieces from the same material several times.
You can use the same dye multiple times, so if you prefer, you can store it in a plastic container after the first try
Step 10. Place the object in boiling water for 30 minutes to set the color
Heat the water in a saucepan. Dip the object inside. The heat will set the dye, but will also cause it to fade slightly. This is another reason why it is best to give it a try first.
Step 11. Let the metal cool
Remove it from the hot water and place it on a napkin to cool for a few minutes. Once it is completely cool, it will have absorbed the new color permanently.
Step 12. Clean all tools and containers with the sodium bicarbonate neutralizing solution
Rinse everything off and make sure no acid remains on the tools it came into contact with during the anodizing process.
Method 3 of 4: Patinating the Metal
Step 1. Prepare the mixture
There are various procedures for patinating metal. Essentially, this method changes the color by a chemical reaction that creates a colored coating on the surface. If you want to give it an antiqued look, similar to the color of the Statue of Liberty, you can use this system with any copper or bronze object. To get the color you want, look for precise instructions based on the metal you intend to patinate or buy the color in-store.
- To make a verdigris coating, combine 3 parts of apple cider vinegar and 1 part of salt.
- If you want a black coating, add the liver of sulfur to the warm water.
- Some recipes tell you to heat up the metal before patinating, so you may want to buy a gas burner.
Step 2. Fill a container with the blend you created
You can use a regular paint bucket if the solution is cold, while you may want to use a large metal pot if you need to heat it. Any type of container must be large enough to hold the object along with the solution. You will likely need to heat or cool it, so use a container suitable for the temperature recommended in the instructions you are following.
- Some chemicals can produce dangerous fumes. Always work in a well-ventilated area.
- If you need to paint a large object that leaks out of the container, you can pour the solution into a spray bottle and spray it on the surface. You can also pour it on a rag and rub it or apply it with a brush. Just be sure to wear rubber gloves when handling chemicals to avoid direct skin contact.
Step 3. Dip the object into the mixture
Put on a pair of rubber gloves and place the metal object inside the container containing the coating mixture. Depending on the instructions you are following, you will probably need to let it soak for a few minutes to several hours. Schedule an alarm and wait.
Step 4. Remove the object
Check it once the time is up. If you want a deeper color, leave it in for longer. Put on a pair of rubber gloves and remove it from the solution when it looks the way you want it.
Step 5. Let it dry completely
The coating will continue to change as the metal dries, so be patient. If you want to color it a second time, put it back into the mixture and repeat the process.
Step 6. Dispose of it
Choose a clear acrylic spray polish to protect the surface and color.
Method 4 of 4: Using Heat
Step 1. Clean the object
Before starting, remove dust, dirt and fingerprints. Wash it with soap and water. Leave it immersed in a degreaser. Then put it to dry on a clean surface.
- Do not take it with your bare hands after washing it. Finger fat can also affect the final color effect.
- It is not possible to predict what shade the metal subjected to heat will acquire. Color varies according to temperature, humidity, time taken and alloy.
Step 2. Turn on a heat source
You can use this method on any object containing copper or iron, such as steel. A smaller, more concentrated flame, such as that produced by the Bunsen burner or a torch, will give a noticeable chromatic variation. On the contrary, with an open flame the variation will be smaller. Depending on the temperature reached by the metal, you can create a color that changes from light yellow to blue.
- Use a pair of pliers, a wrench, or similar tool to hold the piece of metal in order to avoid direct contact as it gains heat.
- If you have an oven, you can use it to heat the item and give it a more even hue.
Step 3. Put the metal piece on the flame
There is not much you can do to manage the color shades it will come to assume. You can only control the extent to which it dyes based on the time it is exposed to heat. You will notice that the color will change as it cools. For example, red could turn into a purple-to-violet color.
- Make sure you heat the metal in a well-ventilated area.
- Be careful not to burn yourself. Put on a pair of work gloves.
- If the flame is thin and the piece of metal is large enough, you can make color schemes of various shades.
Step 4. Let it cool down
Turn off the flame or heat source. Then put the object in a safe place, such as on a concrete floor, so that it cools down. You may want to keep a bucket of cold water handy to dip it in and let it cool down quickly.
Step 5. Coat it with polish or wax
If you are treating a piece of jewelry or valuables, you may want to apply a sealant to give it extra shine and coverage. Once cooled, apply a layer of beeswax or clear acrylic sealant to preserve color and protect the surface. Finally, let it dry.
Advice
- Apply a second coat of primer only if the first is patchy or patchy.
- Work in a well-ventilated, dry and warm (not hot) place.
Warnings
- Sulfuric acid is dangerous. Follow the safety instructions and take appropriate precautions.
- Use safety equipment as you smooth, paint and handle chemicals.
