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Brick Cleaning Specialists — brick cleaning and pressure washing, Warilla NSW

External iron sources

Rust Stain Removal

Orange to red-brown staining running from a fixing, a garden bed, a downpipe or a piece of metal furniture. Rust is one of the most treatable masonry stains there is — provided the first thing tried was not hydrochloric acid.

Looks like

Orange, red-brown, running streaks

Found on

Brick, concrete, pavers, stone, tile

Our verdict

Very treatable with correct chemistry

Quick answer

How do you remove rust stains from concrete and brick?

Rust stains are removed with an oxalic acid or reducing-agent treatment that converts iron oxide into a soluble compound so it can be rinsed away. Hydrochloric acid should not be used — it reacts with iron oxide and typically drives the stain deeper and sets it, making a treatable stain permanent. The metal source must be removed or sealed first, otherwise the stain simply returns.

At a glance

Correct chemistry
Oxalic acid / reducing agent
Wrong chemistry
Hydrochloric — sets the stain
Common sources
Reo, tie wire, fertiliser, furniture, bore water
First step
Remove or seal the iron source
01

Find the source before you clean

Rust always comes from somewhere, and cleaning without removing the source means doing it again next season.

  • Reinforcement and tie wire — offcuts left in mortar joints or too close to the face on new work.
  • Fertiliser — iron-based lawn products flicked onto a driveway or path by a spreader or mower.
  • Metal furniture and pot feet — outdoor settings, BBQ legs and planters standing on concrete or tile.
  • Bore and dam water — irrigation with iron-rich water leaves a stain wherever the sprinkler throws.
  • Downpipes, brackets, air-conditioner frames and balustrade fixings that have started to corrode.
  • Steel lintels above windows, which rust and stain the brickwork below as they expand.
02

The chemistry that works

Iron oxide is not soluble in water, which is why scrubbing achieves nothing. It has to be chemically converted into a soluble iron compound so it can be flushed out of the pores. Oxalic acid and proprietary reducing treatments do this well and are safe on most masonry when correctly diluted and neutralised.

Hydrochloric acid does the opposite. It reacts with the iron and tends to fix and spread the stain, which is why so many DIY rust attempts finish with a bigger orange patch than they started with.

Do not guess this one

Not sure if it’s rust staining?

Several of these stains look similar and want completely opposite chemistry. Using acid on the wrong one turns a removable stain into a permanent one. Send a couple of clear photos in daylight — one close, one of the whole wall — and we will tell you what you are looking at.

Text photosCallor use the quote form

FAQ

Rust — questions we get asked

Will rust stains come out of concrete completely?

Usually, and often entirely. Fresh stains come out easily. Long-standing stains that have soaked deep into unsealed concrete may lighten dramatically rather than vanish, and typically need repeat applications.

Why did my rust stain get worse after I treated it?

Almost certainly hydrochloric-based cleaner. It is what most hardware store masonry cleaners contain, and on rust it sets rather than removes. The stain can normally still be treated afterwards, it is just harder.

How do I stop it coming back?

Remove or seal the iron source, keep iron-based fertiliser off hard surfaces, put feet or pads under metal furniture, and where irrigation water is the culprit, adjust the sprinkler throw or filter the supply.

Identify it

The other eight stains

Efflorescence

White, powdery, fluffy

Calcium & Lime

White, hard, crusty or glassy

Vanadium

Yellow, yellow-green, olive

Manganese

Brown, grey-brown, tan streaking

Acid Burn

Bleached, yellowed, patchy, exposed aggregate

Iron Staining

Orange-brown, diffuse, blotchy

Mould & Lichen

Black, green, grey-white patches

Fire & Smoke Damage

Black soot, brown scorching, tar film

Keep reading

Related work

Iron Staining

Read more

Concrete Cleaning

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Driveway Cleaning

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Brick Cleaning

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Next step

Rust — get it looked at properly

Twenty years of masonry stain work across Sydney and the South Coast. If it can be removed, we will tell you how. If it cannot, we will tell you that too.

0448 882 780Free quote