How We Remove Rust Stains

Rust stains on your painted surfaces, vinyl, and concrete can make your property look neglected and aged. In this guide, we'll teach you the professional methods and acid treatments needed to safely eliminate stubborn rust. For expert results without the risk, trust Tampa Bay Soft Wash in Clearwater, FL to restore your exterior surfaces.

Precautions when working with Acids

First, we want to list some precautions when working with acids. When using some of these acids they can cause severe burns, inhaling its fumes can burn lung and nose lining, and eye contact can cause irreversible eye damage or blindness. It can also be lethal, so it needs to be treated and handled as such!

Keep away from children.

If ingested, drink water to dilute the strength and contact your local Poison Control Center .

When acid is used protective eyewear, gloves, and a respirator are required.

If in contact with skin or eyes, rinse thoroughly with running water.

Ventilation is required when working indoors.

If inhaled, move the person to fresh air.

Do not apply acid to dry surfaces. Always wet surface prior to application, including any adjoining areas.

Do not allow the surface to dry with acid still on it.

Use caution when applying acids to avoid contact with other surfaces, such as wood or metal, as an unwanted reaction and discoloration of surfaces can occur.

Avoid contact with vegetation. Excess solution should be diverted away from grass, trees, and shrubs.

When diluting, always introduce the acid to the water, not the water to the acid.

Do not mix acid with any other chemicals.

Always have a bottle of acid neutralizer on hand in case of an accident.

Work with a hose or large container of water nearby to wash skin in case of accidental splashing.

All Big Box Store Rust Stain Removal Products Utilize Acid

Now that I have scared you, don’t worry about using acid for your rust stain removal project, just know that all big box stores, such as Lowes and Home Depot, sell rust removal products that contain acid. Every product that is sold in America has a MSDS (material safety data sheet). If you take the time, you can see exactly what acids are in each of these product. Some of them use multiple acids, while others use a single acid. Some suggest the percentages of the active ingredient are “proprietary” but at least you will know what type of acid it is utilizing.

Common acids that Remove Rust Stains

If you were to look at all of the MSDS sheets of these retail rust removers you will notice that the most common active ingredient is oxalic acid, which is considered somewhat safer compared to other acids. However, you will also see hydrofluoric acid, sulfuric acid, muriatic acid, phosphoric acid, among others. As an example, RustAid by Goof Off utilizes 10% oxalic acid and 0.05% hydrofluoric acid according to the MSDS . The bottom line is that all rust removers, like many chemicals, is only safe in the hands of a well trained technician or homeowner.

A fun fact is that Coke, Pepsi, RC, and many other dark soft drinks use phosphoric acid for their sharp flavor and to extend shelf life. These soft drinks can all be used to remove light rust…

What Acids We Utilize

At Tampa Bay Soft Wash & Pressure Cleaning we decided to mainly utilize oxalic acid in dry form and a retail product called Acid Magic in liquid form for our rust removal S.O.P. Both products have pros and cons that I will touch on. In certain circumstances, such as battery acid stain removal, we will utilize various products from Front 9 Restoration , however, their product lineup deserves its’ own blog.

Acid Magic works extremely fast and can be bought locally from Ace Hardware! Muriatic acid, a less-pure variant of hydrochloric acid, is a very aggressive and noxious acid. Acid Magic is a form of muriatic acid that has 90% less fumes and will not burn you if it comes into contact with your skin. However, it still shouldn’t come in contact with mucous membranes (eye, nose, and mouth). While this product comes with a higher price tag than oxalic acid, this is a very quick, effective, and safe option for home and business owners.

Oxalic acid is very cheap in raw/dry form. In dry form it is stable and has an extremely long shelf life, years if stored correctly! You can create whatever dilution that is required, up to a 75% strength “paste” if so desired. While still dangerous, oxalic acid is widely considered to be one of the safest options for removing rust. However, it will not remove all rust stains and takes longer to work.

Solution Dilution

Dilute 1 part Acid Magic to 4 parts water as a starting point. A 1:4 dilution ratio means that a simple dilution contains one part concentrated solution or solute and four parts of the solvent, which is usually water. As an example, if you planned on diluting a whole gallon of Acid Magic with a 1:4 dilution ratio, you would fill a 5 gallon bucket with 4 gallons of water and then add the 1 gallon of Acid Magic, giving you a total of 5 gallons of diluted solution. You can make the solution stronger as needed. I use a 1:1 ratio for tough stains. I have even used it undiluted/full strength, it all depends on the scenario and the desired results.

Dilute 1 cup (8 ounces) of dry form oxalic acid with 1 gallon of warm water as a starting point. I like to use 2 cups of dry oxalic acid to 1 gallon of warm water for tougher stains and adjust as needed. If you’d like to create a paste, use 3 parts oxalic acid to 1 part water, a 3:1 ratio. A paste can be used to aggressively attack a specific rust spot without spreading to other areas!

Apply, Dwell, Rinse, Neutralize

Application is the same for both oxalic acid and Acid Magic.

Pre-wet all surfaces that may come into contact or get hit with overspray or runoff.

Evenly apply diluted acid with a pump sprayer.

Let dwell for 5 to 10 minutes and asses the results.

Do not let it fully dry, mist with water or reapply solution.

If you do not have the desired results, make a stronger solution and repeat the steps as needed.

Thoroughly rinse off all of the surfaces that the acid may have come into contact with.

If acid comes into contact with something unintentionally saturate that area with acid neutralizer and thoroughly rinse the area with water.

Acid Neutralizer

Keep a supply of  baking soda  or garden lime nearby in case you need to quickly neutralize acid. While sprinkling these substances full-strength will work, the best plan is to mix ½ cup of baking soda and a quart of water in a spray bottle and keep it nearby.

How To Properly Discard The Remaining Acid

To discard your acid solution, pour baking soda in it. The solution will bubble, so keep pouring it in until it stops bubbling. If you want to be sure, you can use a pool test kit to measure the pH. You’ll want to make sure it reads higher than 7 on the pH (7.5 is a good target). At this point all of the acid will have converted to a salt form, which is safe and harmless. As a precaution though, I would dump it outside somewhere away from where my pets have access and not down any drains.