Acid etching & pre-paint prep

[Craig 111]

What would you recommend as the most efficent and cost-effective way to acid-etch concrete before painting? What is your method of application, do you neutralize with another chemical or just plain water?

[One Tough Pressure 580]

Craig,

If you use an acid, it is best to neutralize it so you know that their will be no product failure from any acid that may have been left behind.

I have done a few paint preps for people that were going to apply the paint themselves. I use my vacuum surface cleaner and only use chems when needed to get things that 210° will not.

Some of my first floors were prepped in May of 2003 and they are still doing just fine without the use of acid.

[Celeste 341]

What kind of painting are you doing? When we applied the acrylic stain to the driveway we did (which rolled on like paint) we etched with muriatic (4:1) : water - Rinse well - let dry completely then rolled on the product. We have pics of the driveway if you want to see - give us a call :) Application method was rolling, however, you can pick up a cheapo Wagner sprayer (build the $70ish into your bid) use it once and ditch it. Spraying will give you a more even application but if you must roll - get an 18" roller....it goes much faster.

Celeste

[Craig 111]

Thanks for the replies.

Here's what I've found out so far.

1. Steam Clean it.

2. Apply Oxalic mixed 8oz/gallon, let dwell 10 minutes.

3. 25 degree or turbo nozzle the concrete again to get desired degree of etching.

4. Neutralize

I'd really like to stay away from muriatic if at all possible and am trying to find an alternative. What do you think of this?

[Pams Pressure & Clean 64]

My understanding is that the hydrochloric is necessary to ensure a complete strip of the topmost layer of concrete, thus ensuring the cleanest surface possible for the new coating to adhere to. Additionally, the acid helps to roughen the surface, again making a more complete and/or stronger bond possible.

All this is based on what I have read and gathered from folks I know who actually do this work. I persoanlly have never done it, but it appears that it is pretty straightforward.

I have no idea on whether the oxalic would produce the same, similar, or acceptable results...

[Celeste 341]

I'd really like to stay away from muriatic if at all possible and am trying to find an alternative. What do you think of this?

When cleaning concrete...yes the idea is to clean and not etch, thus the avoidance of muriatic. Muriatic is supposed to etch concrete which is what you're trying to accomplish, right?

Oxalic is not going to etch concrete without applying it at a horrific strength and that's going to cost you plenty. Using a certain degree tip to etch the concrete...I'm thinking that if you're asking what to use chemically, eyeballing the surface to see how much of the top coat you're taking off with a nozzle is not going to be your best method. Prepping concrete using the KISS (Keep It Simple Stupid - not saying that you personally are stupid by any means) system is the most efficient and cost effective way to do it.

Roger doesn't like to use muriatic acid either, but for purposely etching concrete .....it's the way we do it.

Celeste

[Craig 111]

Ok.

Thanks Celeste. That's pretty much what I figured as the muriatic will work faster and stronger. I may just buy a throw-away pump up sprayer to use as the job is pretty small-just a double car garage. It's my first acid etch and faster is better... time is money. And again I am still think that being such a strong acid, it's better to neutralize with R-109 just to be safe after rinsing.

Thanks,

Craig

[Craig 111]

Ok, jobs done, came out perfect and here's what worked. Remember that this concrete was 40 years old and VERY hard, so I needed a strong acid to eat at it quickly. There were a lot of old oil and rust stains.

1. Power wash concrete to clean it. (water only no degreasers as they will neutralize the acid.)

2. Mix 50/50 Muriatic with water in bucket.

3. Apply with x-jet nozzle at 2:1 so final HCL dilution is 4 to 1.

4. Let dwell for 10 minutes

5. Neutralize

6. Power wash with surface cleaner

The oil and rust were 95% gone, concrete sparkled and had a very nice uniform etching