How to Blacken Aluminum

Arc and Anvil may collect a share of sales or other compensation from the links on this page. This comes at no additional cost to you, and all the prices and availability are accurate at the time of publishing.

While aluminum is a strong and versatile material, it does have its limitations. That said, you can improve this metal by adding a layer of black anodized coatings. Not only does blackening aluminum make it look better it also helps protect it from the elements. 

If you’re interested in blackening your aluminum parts, we’ve curated the steps necessary. Keep in mind that you will need safety equipment and a reliable power source to get it right. Here’s what you need to know. 

How to Blacken Aluminum

Step One: Clean the Surface

Dawn Ultra Dishwashing Liquid Dish Soap (4x19oz) + Non-Scratch Sponge (2ct), Original Scent (Packaging May Vary), Combo pack

Make sure to wipe off any dirt, dust, or other contaminants. The piece of aluminum should be smooth and shiny. If the part is old, it may be tarnished. Don’t worry; the next step will clean it even further. Dish soap works perfectly for this step. 

Step Two: De-Smut the Aluminum

De-smutting means removing all non-aluminum contaminants. This step is crucial because it will ensure a better bond between the anodized material and the metal. If you skip this step, you’ll get uneven results that won’t last as long. 

You can buy de-smutting liquids online. Typically, you’ll have to leave the aluminum submerged for about two minutes. Be sure that you buy enough liquid and have a sufficiently-sized container for both it and the aluminum piece. You can also de-smut multiple pieces in the same solution. 

For best results, we recommend heating the liquid to 140 degrees Fahrenheit before submerging the metal. 

Also Read: How To Blacken Steel With Beeswax

Step Three: Mix Sulfuric Acid and Distilled Water

LabChem LC256602 Sulfuric Acid, 0.02N (0.01M), 1 L Volume

Deer Park Brand Distilled Water (1 Case (6 Bottles))

Sulfuric acid is a bit harder to find, and you need to treat it with the utmost care. Always make sure that you’re wearing safety goggles and gloves when handling this acid, as it’s corrosive to human skin. One drop can leave a significant chemical burn. 

Mix one part sulfuric acid with one part distilled water. For the uninitiated, distilled water has had all contaminants and minerals removed by the distillation process. So, you can’t just use regular tap water or drinking water for this step. 

Another safety tip to follow is to add the acid to the water, not the other way around. This way, splashes won’t be as caustic and won’t create as much damage. To ensure that you have a correct mixture, measure each ingredient separately first. 

Step Four: Attach a Negative Cathode to an Aluminum Plate

You will need a power source with a positive and negative wire (like a car battery). However, you need to be able to turn this power source on and off, so a battery won’t work because the current will flow automatically. 

Connect the negative end to an aluminum plate and submerge it into the acid solution. Still wear goggles and gloves as diluted acid is still dangerous. 

Also Read: How To Polish Aluminum

Step Five: Connect the Positive Cathode to the Aluminum You’re Blackening

Use aluminum wiring to make this connection. Then, dip the piece into the acid solution. 

Step Six: Turn On Your Power Supply

Make sure that the electricity is flowing at 12 volts and two amps. Any higher than that and you can cause a dangerous reaction and damage your aluminum piece. 

You can tell when power is flowing through the solution when bubbles form at each cathode. Once the bubbles stop, you can turn the energy source off and remove the aluminum. At this point, the metal is ready for anodization. 

Step Seven: Create a Blackening Solution

You’ll need to mix four ounces of blackening dye with two quarts of distilled water. For best results, we recommend heating this solution to 100 degrees Fahrenheit. Doing this will help the dye adhere to the aluminum better. 

Step Eight: Dip the Aluminum Into the Dye

Fully submerge your aluminum piece for about 15 minutes. Afterward, you can pull it out, and it should be completely blackened. 

To seal the anodized coating, you’ll have to boil the piece in pure distilled water for about 30 minutes. This step will ensure that the coating won’t flake off. 

FAQs About Blackening Aluminum

Can Materials Other Than Aluminum Be Anodized? 

Yes, you can anodize other metals, such as magnesium, titanium, and zinc. Other metals like iron and steel can’t be anodized because the coating will simply flake off as the material oxidizes (rusts). 

How is Color Added to Metal Anodizing? 

Dyes work well with anodizing because aluminum is porous. During the anodizing process, the dye fills in each pore. Once you seal the coating, you can’t remove the coloring.

The Final Word on Blackening Aluminum

Although this process is relatively complex, it offers superb results. Not only can you color your aluminum with different dyes, but you can also protect it from damage. Overall, blackening aluminum makes it so much better. Just make sure to practice safety at all times!


Sharing is caring!

Leave a Comment