Removing Rust with Wet Sandblasting

Whether you’re cleaning car parts, restoring a vintage tool, or removing corrosion from a motorcycle engine, using a wet blast cabinet to remove rust is often the most practical solution.

There are other ways to remove rust and corrosion from parts and tools (which we will examine shortly). However, these can often be time-consuming or labor-intensive.

For large scale production shops, where you need to remove rust from many parts on a consistent basis, wet blasting is the optimal solution. We’ll look at the various methods for removing corrosion from metal objects, and show pros and cons for each, as well as advantages and disadvantages of dry sandblasting and wet blasting.

Finally, we look at why vapor blasting is the one of the best rust removal methods. Also, we’ll discuss the ideal set up for wet blasting rusted parts to remove corrosion and prevent flash rusting from occurring afterwards.

Common Methods of Rust Removal: Pros and Cons

Vinegar Soak Method

One of the most common ways to remove rust from small objects is to soak them in vinegar, and then remove any excess oxidation with a wire brush. This works because vinegar is 5 to 20% acetic acid by volume.

Pros: This is an inexpensive, low effort way to remove rust from small objects.

Cons: It is time-intensive and doesn’t work at scale. You must soak the rusted objects for a couple of days to turn the rust into removable oxide. This method is also inefficient or anything more than singular tools or parts. If you are looking to remove rust quickly from a large amount of parts, or from larger objects, the vinegar method is not an option.

Using Electrolysis for Rust Removal

Like the vinegar soak method, electrolysis is a process that takes some time, and is best for small batches of parts.

In electrolysis, a container of water mixed with Arm and Hammer washing soda is prepared. An anode of sacrificial steel (like a coffee can) is set up. This anode must be big enough to surround the rusted part. The rusty part is suspended from a wooden board or pole and submerged in the baking soda solution. Leads are connected to the sacrificial anode and the rusty object, which are then connected to a car battery. The electricity running through the conductive solution “cooks” the rust off the object. The result is a rust sludge that floats to the top of the washing soda solution.

Pros: Electrolysis can be set up with objects you have laying around the house.

Cons: If you accidentally hook up the wrong polarity of the battery to the anode/rusty part, it will chew up the part you are trying to clean. Electrolysis takes 15 to 20 hours to work, and is not practical for high volume of rust removal. The chemical process of electrolysis breaks water down into hydrogen and oxygen, which means that if you use this method, make sure you are doing it in a well-ventilated area to prevent explosions.

Evapo-Rust, an Off-the-Shelf Chemical Solution

Evapo-Rust is a rust removing liquid that works similarly to the vinegar soak method. Rusty parts are soaked in the liquid overnight, and then washed off.

Pros: Soaks into nooks and crannies, and works more effectively than vinegar or other acids. If you are trying to preserve existing paint or coatings on smaller parts, this may be a viable solution.

Cons: You must soak parts overnight, and you must have a container big enough to submerge the rusty parts completely. You also need to apply a rust inhibitor afterwards to prevent rust from reappearing.

Why Wet Blasting is a More Practical Method for Rust Removal

You may have noticed that there are some things in common with the rust removal methods we’ve discussed so far. They take a long time to work, and they are only practical for smaller objects, or a small amount of parts.

If you have a continuous stream of parts that need to be cleaned, whether that’s rust or corrosion, the methods we’ve discussed so far simply aren’t feasible.

Dry sandblasting is certainly an option, it certainly is quicker than soaking parts for days in solutions. But the biggest drawback to dry media blasting is that small particles of abrasive can get lodged in crevices in the substrate. You can always cover sections of the blasted object with aluminum tape, but that isn’t a 100% failsafe, as the tape is also getting blasted.

There’s one other detriment that people will mention with dry blasting rusted surfaces. Friction heat from the abrasive can warp the metal surface, if it is thin.

Wet blasting with a mild abrasive is the perfect solution if you need to blast a larger volume of objects, with speed, and remove rust effectively. The water simultaneously prevents warping caused by frictional heat, while cleaning the substrate.

Let’s look at some of the abrasive media you may choose to remove rust from your parts.

Best Abrasive Media for Removing Rust in Wet Blasting

It is important to note that rust and corrosion doesn’t occur in an even pattern. Rust and oxidation develop in peaks and valleys, and when you remove the rust from metal, you may notice a phenomenon known as pitting. These is small dimples that are left in the substrate, particularly in ferrous metals.

If you are blasting aluminum, plastic media, walnut shell, or glass beads are the best choices. These have a lower Mohs hardness, so the metal surface isn’t devastated.

For steel or iron, glass beads or aluminum oxide is a good choice, especially if you want to take it down to bare metal. Keep in mind that aluminum oxide has a very high Mohs hardness.

In most cases of corrosion removal, we’ve found that a mix of glass beads and sodium bicarbonate strikes a good balance of removing rust, while leaving the substrate intact.

It’s a good idea to add a rust inhibitor to the slurry blasting mix while wet blasting. You can also apply a protective coating right after stripping the rust. This will prevent flash rusting from appearing on the metal surface after eliminating the initial rust.

Summary

Though there are different ways to remove rust from metal objects, wet blasting is the fastest way to eliminate corrosion at scale. Using a mix of glass beads and sodium bicarbonate works well for most ferrous alloys. Use a rust inhibitor in the slurry mix, or apply a permanent coating afterwards to prevent rust from reappearing.

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