Acid Etching Concrete: Choosing and Setting Up the Sprayer

Acid etching concrete is an acid job, so the sprayer needs VITON (FKM) seals and acid rated parts, sized to the area you are etching. Brick, concrete and paving acid washes are usually hydrochloric acid based, and that attacks the seals and metal parts in a garden sprayer or a sealer sprayer. Match the sprayer to the acid and its strength, let the acid maker's label and SDS run the process, and keep a seal kit on the shelf.

What acid etching is, and where the sprayer fits

Acid etching uses a dilute acid to open up smooth or dense concrete so a sealer or coating can grip. The same acids wash cement haze, mortar and efflorescence off brick, pavers and tiles. Our guide to applying concrete sealer with a sprayer covers the coat that goes on afterwards. This one covers the acid step before it.

Why it has to be an acid resistant sprayer

Our compatibility data rates brick, concrete and paving acid wash for the acid resistant sprayer with VITON (FKM) seals, and notes these products are usually based on hydrochloric acid, the same acid sold as muriatic acid or spirits of salts.

• The seals. VITON is the seal for acids. EPDM suits bleach, chlorine and caustics, and our data does not rate it for hydrochloric acid.
• The metal parts. Gloria's standard PRO5 has a stainless spring and a brass lance, which acids attack. The acid resistant AR5 uses an acid resistant spring, a PVC lance, a nylon trigger and a PVDF nozzle instead.
• Not the sealer sprayer. The stainless Gloria 505TK and 510TK Concrete Sealer units and the Volkanex 12L sealer sprayer are listed as not for acids, so etch and seal is a two sprayer job.
• Heat. Klager and the Gloria AR5 manual both say not to fill liquid hotter than 30 degrees C.

What the compatibility data says about etching acids

These ratings come from our Chemical Compatibility Guide. The percentage is the strength of the liquid in the tank, which your acid maker's label sets. Check section 3 of the SDS for the acid, then read across.

Acid	Strength	Rating	What to use
Hydrochloric (muriatic acid, most brick and concrete acid washes)	Up to 10%	Suitable	Acid resistant sprayer, VITON seals
Hydrochloric	10 to 25%	Conditional	Sources differ (25% and 10%), so ask us to confirm the model
Hydrochloric	25 to 30%	Ask us	Klager rates only its Master Acid+ specialist model to 30%
Hydrochloric	Above 30%	Ask us	No source rates a sprayer for this
Phosphoric or citric	Up to 30%	Suitable	Acid resistant (VITON) or alkaline resistant (EPDM) sprayer
Hydrofluoric, or any acid or blend not listed	Any	Ask us	Send us the SDS before you fill

The ratings apply to the Klager acid models. The Gloria AR5 shares the VITON seal but is a different build, and its manual lists hydrochloric acid up to 10%.

Poly, stainless or air driven: size it to the floor

Once the seal is right, size the sprayer to the area.

• Test patches, edges, steps and mortar smears. A Klager 1.2L or 1.5L Acid Resistant pressure sprayer. The 1.2L holds 1,200 mL at 3 bar. The 1.5L holds 1,500 mL at 4 bar.
• Garages, paths, single slabs and brick walls. The Gloria AR5, a 5.0L acid resistant poly sprayer working at up to 3 bar (44 psi), with a PVDF flat fan nozzle that lays down an even band.
• Large floors and continuous work. An air driven unit that pumps ready to use, premixed solution straight from the drum or IBC, off compressed air. The Meclube IBC mount sprayer sits on the IBC with a 12.5 m braided hose. The Flojet wall mount box sprayer has a double diaphragm pump with VITON elastomers, a 15 m hose and a regulator preset at 4 bar (60 psi), the level we recommend for acid application.
• Stainless. Keep it for the sealer. Our stainless sealer sprayers are built for sealers and solvents, and their data sheets say they are not suitable for acid based products.

For your own pump and hose, the CT Italy acid resistant trigger and lance carries VITON seals. Send us the SDS and fittings to confirm it suits your acid. The full range is in concrete and cement removal sprayers and acid resistant sprayers.

The etching process, step by step

This is the order of work, not a recipe. Dilution, dwell time, neutraliser and protective gear all come from the acid maker's label and SDS.

1. Prepare. Clean the surface, protect anything the label says the acid can damage, and wear the protective gear the SDS lists.
2. Wet. Wet the concrete with clean water first if the label tells you to.
3. Apply. Mix to the label, fill the sprayer no higher than its mark, and lay an even coat in sections you can manage.
4. Dwell. Leave it for the time on the label, and no longer.
5. Neutralise. Use the neutraliser the acid maker names, the way they say to.
6. Rinse. Rinse thoroughly with clean water, and deal with the rinse water the way the SDS and your local authority require.
7. Test. Check the surface the way your sealer or coating maker specifies, and let it dry to their spec before you coat.

We do not publish dilution rates or dwell times, because they belong to the acid maker and change from product to product. Once you have the rate from the label, the Dilution Calculator turns it into mL of concentrate and water for your sprayer size.

Walls and vertical surfaces: when to foam

A liquid spray runs off a wall or panel before the acid has done its work. Foam clings to vertical surfaces and stays in contact longer. NORA PRO supplies genuine Lafferty Acid LC Foamers, in one way and two way versions, for fixed stations in wash bays, plant rooms and processing areas.

They mount on the wall and run on mains water pressure from 2.8 to 8.6 bar plus compressed air. Colour coded metering tips set how much acid the injector draws, a regulator takes the foam from wet to dry, and the fan nozzle throws up to 3.7 m. See Lafferty acid foamers and sprayers.

Our hand pump Washfoam foamers have EPDM or NBR seals, not VITON, and our data does not rate either for hydrochloric acid, so ask us before you foam an etching acid by hand.

Looking after the sprayer after acid

Klager says a sprayer on the harshest chemicals lasts 3 to 6 months at best. Good habits stretch that out.

• Depressurise first. Release the pressure before you open the tank.
• Do not store acid in it. Decant what is left back into its container, rinse with clean water unless the SDS says otherwise, and pump water through so the pump and nozzle come clean.
• Store it right. Depressurised, out of heat and direct sun.
• Reseal, do not replace. When it weeps or loses pressure, fit a genuine VITON seal kit: the Klager VITON kit for the 1.2L and 1.5L Acid Resistant, or the Gloria complete VITON seal kit for the AR5. See parts and seal repair kits.
• Label it. One sprayer per chemical family. A Klager colour coding cap marks the acid bottle so sealer or solvent never goes in it.

The full routine is in our Refill and Repair Guide. For the rest of the slab job, see concrete and construction and concrete, tile and stone sealing sprayers.

Frequently asked questions

What sprayer do you use for acid etching concrete?

An acid resistant sprayer with VITON (FKM) seals and acid rated parts: a Klager 1.2L or 1.5L Acid Resistant for small areas, the 5.0L Gloria AR5 for slabs, or an air driven Flojet or Meclube unit for large floors.

Can I use my concrete sealer sprayer for acid etching?

No. The Gloria 505TK and 510TK Concrete Sealer units and the Volkanex 12L sealer sprayer are listed as not for acids, so use a separate acid resistant sprayer for the etch.

What strength of hydrochloric acid can go in an acid resistant sprayer?

Up to 10% is suitable in a VITON acid resistant sprayer. From 10 to 25% ask us to confirm the model, from 25 to 30% only Klager's Master Acid+ is rated, and above 30% no source rates a sprayer.

How long do you leave acid on concrete before rinsing?

As long as the acid maker's label says and no longer, because dwell time, dilution and neutraliser vary from product to product.

Can I spray brick cleaning acid with the same sprayer?

Yes. Brick, concrete and paving acid washes are rated for the VITON acid resistant sprayer and are usually hydrochloric acid based, so the same strength limits apply.

Concreters, builders' cleaners and chemical resellers who supply etching acid can request a quote for acid resistant sprayers, foamers and seal kits in volume, or apply for a trade account. NORA PRO is the exclusive Australia and New Zealand distributor of Klager.