Acid etch concrete

[andeep]

I have had a fresh pour of concrete in my garage that has had 3 weeks to dry so I decided to acid etch the floor so I could put on my sealer and epoxy paint.

I bought 5 litres of the following:

http://www.transtools.co.uk/store/p...ar-acid-etch-for-concrete-floors-5-litre.html

It states that it will cover 7m2 per litre, so 5 litres should cover 35m2 which is more than enough for my garage.

So I poured it into a plastic watering can with a rose head and poured it on the concrete, but I only managed to cover something around 5m2 with the entire 5 litres of acid, which is ridiculous.

What am I doing wrong here? I applied to dry concrete and made sure that every cm was damp with the acid, then broomed it around. Should I wet the concrete and apply it sparingly, then broom it around to cover all areas? Or did I have the right idea of flooding the floor with it?

Thanks guys

 

[Fastback]

Im confused, did you get results where you did spread the acid? If not did you strip the clear or sealer off the floor first?

 

[munkey]

Also, does it say to dilute it or something like that? I know this is an obvious question, but... what if you spread it thinner? (I doubt many Americans are going to be familiar with that exact product. At first glance it looks to be some sort of formulated liquid and not the raw hydrocholoric acid dilution that some of us have used.)

 

[andeep]

Nope didn't have any instructions to dilute it. Product is rubbish and doesn't do the job properly.

Instead I am going to buy hydrochloric acid and mix it with water. I can get hold of 36.2% hydrochloric acid, is that okay? How much do I need to dilute it by?

 

[bigdav160]

Cut it in half with water. How big is your pad?

 

[Edger]

It might be worthwhile doing a test with the acid first. Mix it 10:1, 5:1, 2:1 and spread a strip of each to see how it reacts. All you need is a good fizz and a surface that has no polish left after rinsing. Hopefully 10:1 will work well, 2:1 is overkill unless the slab is very hard. Leave the acid on for 10 mins before rinsing because sometimes with harder concrete the 10:1 solution takes a bit longer to do the same job as 5:1 does quickly.

 

[ZRX1040]

Just in case you didn't know, ALWAYS add acid to water. DO NOT add water to acid or it can spatter violently. Get a respirator if you dont have one.

 

[Edger]

You do not have to use a respirator, (if you have a death wish) just smile while working and it will clean your teeth for you!

 

[andeep]

I am following this video:

He has stated to use a 10:1 ratio, but I will do a test to see what works best for me. Alphagarage has said the following on another thread which I will use:

Different strengths of the bottled acid, different concrete compositions and conditions, these factors make it impossible to predict how much acid will be needed to properly profile a floor. So to figure out what works for your floor run a quick test or two.

First read all package instructions and warnings, muriatic acid is one of the most hazardous products sold retail, it is caustic and toxic, so wear protective gloves, face coverings etc.

Your floor should be thoroughly cleaned and degreased beforehand with no sealers or previous coatings.

Pre-wet the floor so that it's damp, not standing water, just evenly moist without puddling.

Now to test for the correct strength - Start out with a mix of about 1 part acid to 3 parts water (always pour the acid into the water - slowly!), just a small amount, say 1/2 cup acid to 1.5 cups water. Pour this on an inconspicuous spot, what you want is a strong enough mix that causes a reaction, fizzing and bubbling, that's the acid reaction with the calcium in the concrete. If the mix just sits there like water, it's too weak; if it smokes and foams, it's too strong. Once you've found the correct mix of acid to water you're set to do the whole floor.

Again make sure the entire floor is damp - not too wet with standing or puddling, just damp.

Have a stiff broom ready (check first to make sure the bristles don't react with the acid), protect any areas you don't want acid to hit, remember that muriatic acid is caustic to metal - even its fumes can damage metal!

Figure you'll have about 15 minutes to work with the acid on the floor, you do not want the acid mix to dry on the floor, so don't etch too much area.

Evenly apply oyur acid/water mix, I like using a all plastic flower watering can. Broom the mix to work the acid into the concrete and promote reaction. The acid will do most of it's work in 10 - 15 minutes, so after about 15 minutes completely rinse the area with water and/or neutralize it with a mix of 1 pound baking soda with 5 gallons of water. If you don't use baking soda, be careful with the run off rinse water and don't let it run onto any landscaping, it may still be a bit "hot".

Repeat the process until the entire floor has been etched. Using a baking soda solution to neutralize the concrete is strongly recommended. A like with the acid solution, do not allow the baking soda mix to dry on the concrete.

When completed your floor should have the texture of 80 - 120 grit sand paper. Some floors will need more than one application of acid to do the trick.

If you want to chemically profile the floor, but can't or don't want to deal with a chemical as harsh as muriatic acid, there are other chemical available. We offer OrganiPrep, far less toxic and smelly, but as effective, but it does cost more.

 

[brtsvg]

Now to test for the correct strength - Start out with a mix of about 1 part acid to 3 parts water

I did it this way while prepping my floor this past summer for epoxy, and the this 3:1 ratio of water to acid worked fine for me. I had enough acid left over to do the etch process twice just in case I missed some spots the first time.

Most of the literature states that when etching a new concrete floor to wait at least 30 days prior to etching and painting, in order to properly cure the concrete first. Dampness in the concrete will work against you when it comes to the paint sticking OK.

 

[andeep]

All done. I used a 3:1 ratio of water to hydrochloric acid (36%). Applied it nice a thick and brushed it in with a stiff bristled broom. Washed it off with a pressure washer and a heck of a lot of water! Spend around an hour washing it down!

These the results (concrete is still wet):

A lot of material was removed by the acid!

But one problem is that there a few holes that have appeared:

They are very crumbly and can dig out bits of sand/aggregate with your finger nail. Why has this happened? I didn't lay the concrete, builders did it. I'm hoping that after the floor is sealed then painted it will be okay?

 

[Interex]

Holy ****, you must have a serious industrial pressure washer or some poor concrete. The acid etch is only designed to create a sand paper like texture to the floor. Looks like you've got a bit further than that! Epoxy would fill those holes but likely not leave enough product to be spread throughout the rest of the floor. I had a few holes in my floor similar to those and filled them with a quality concrete patch and let it cure before laying down my epoxy.

 

[andeep]

The pressure washer isn't powerful at all. Its defo the concrete, the builders that laid it were useless.