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Oxalic Acid Cleaner

rust in acrylic tub shower

This is deep rust staining on an expensive acrylic bathtub/shower unit. Can the rust be safely removed for less than $1? Yes it can! Copyright 2022 Tim Carter

Oxalic Acid Cleaner - It's a Great Rust Remover

Not a week goes by that you, or another reader or two or three or twenty, might reach out to me with a fantastic question about the column of mine you’re reading. Often you might ask why I failed to dive deeper into the topic. You may not realize this, but your newspaper that publishes my column often has a limited amount of space where my words and photos must fit. I need to adhere to that word-limit restriction.

About a month ago this column was devoted to removing rust from my own toilet. I received an avalanche of great questions that were not covered in the column. So many that I felt a follow-up column on rust removal would help you save thousands and thousands of dollars. Let’s get started.

Will Oxalic Acid Hurt Drain Pipes?

The most frequent question of all revolved around two related topics: will the oxalic acid harm the plumbing pipes in my home and how does one neutralize the acid? Weak oxalic acid will not harm PVC or ABS piping. Plastic drain pipes are generally immune from any and all weak acids. Cast iron drain pipes and acids don’t play well together with acid so it’s important to neutralize the acid before you allow it to flow through the pipes on its way to the city sewer or septic tank.

How Do You Neutralize Oxalic Acid?

You neutralize an oxalic acid solution adding ordinary baking soda. Start to pour in some into the solution. It should bubble. Stir carefully and continue to add more soda powder until the bubbling stops. The best way to check to see if the solution is neutralized is to use litmus paper making sure the solution has a pH of 7.0. Adding lots of water to the solution will also dilute the acid.

Will Oxalic Acid Hurt a Septic Tank?

You may have wanted to know if the oxalic acid would hurt your septic tank and the biologic activity inside the tank. Well, we know for a fact it won’t help it! The safest thing to do when cleaning anything using an oxalic acid solution would be to prevent the solution from going down the drain. Capture the acid solution and take it outdoors to pour onto the ground once you’ve neutralized it.

Can you Use Oxalic Acid on an Acrylic Tub or Shower?

Next up I received quite a few questions about how safe it is to clean acrylic tubs and showers, chrome faucet parts, ceramic tile and all sorts of surfaces in a normal bathroom that might have rust stains. I’ve got great news for you. In my experimentation at my own home, I’ve discovered the oxalic acid solution doesn’t harm anything other than polished marble. Keep any and all acids away from marble.

Do a Test First

Here’s the best advice I can offer before you start to apply an oxalic acid solution on anything. Mix up a small amount of the solution and use a cotton swab to apply a drop of the acid solution to the object. Let the acid sit for about an hour. It’s vital that before you apply the drop that the area is clean and dry. It helps that it’s also in an out-of-the-way spot so if the acid does damage the sheen, you don’t notice it that much.

Will Oxalic Acid Clean Vinyl Siding and Concrete?

You may have reached out to me about using oxalic acid outdoors to clean rust from vinyl siding, brick, mortar, concrete, etc. You get rapid results when cleaning vinyl siding but you’ll discover it takes quite a bit of time to get great results on rock, concrete, brick, mortar, etc. This is because the rust can soak into these surfaces. You just have to be very patient and try to work in the shade so the oxalic acid solution doesn’t evaporate.

Oxalic Acid and Redwood

Oxalic acid solutions are the go-to cleaner for exterior redwood. If you recall your high school chemistry, you’ll remember that acidic solutions have a pH lower than 7. Caustic chemicals like many oxidizers have a pH higher than 7. Redwood can turn black or darken if you use anything with a pH higher than 7.

This is why you never want to use chlorine bleach or any other oxidizer to clean redwood. All that said, always TEST using an oxalic acid solution solution to clean your redwood or any other surface. I can’t stress that enough. You can’t hope everything is going to work out fine. It only takes an hour at most to run a test.

Where Can I Buy Oxalic Acid?

Just about everyone who reached out to me asked where’s the best place to purchase oxalic acid. Fortunately it’s a very affordable product and I bought mine online from Amazon. I got a sizable pouch of the white powder for less than $15.00. You may discover a local national-chain hardware store stocks these pouches.

oxalic acid 2 pound bag

This is a re-sealable bag of oxalic acid crystals. Go HERE to get it delivered to your home NOW.

Always read the instructions about how to mix, use and store the unused acid. My pouch is sitting on the bottom shelf of my refrigerator right now next to cartons of milk. Oxalic acid powder likes to be stored cold if at all possible. If you’ve got kids in the house, be very careful where you store it. You never want the possibility of a child thinking the acid is powdered sugar. It looks just like it.

What can I help you with? What issues around your home worry you? What do you want me to discuss in my upcoming columns? Go here and tell me.

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