Muriatic Acid Question vs Sheet Plastic

[Jfile]

I normally drop all of my cut pieces into muriatic acid for about 24 hours to clean the metal good before hitting each piece with a fine grade flap disc. I use the pans that you can buy from Lowes to put under your washing machine. It gives me a "bath" area of around 28" x 30" x 2" deep, and has worked great for me. I built a holding box out of 2 x 4s and plywood so that the trays sit in the box and have a plywood lid over them. I also keep a tarp over the whole set up when not in use and it's outside, away from any of my equipment to avoid issues with the fumes.

I have a few jobs to do that have pieces larger than what will fit into the current containers. I was contemplating building another simple frame out of 2 x 4s with a plywood bottom again but this time just line the bottom of it with sheet plastic since it will be temporary and since I can't really find large plastic pans like those used on my primary setup.

Here's the question .... Does anyone know if the acid would eat through 4 or 6 mil plastic in a 24 - 36 hour period? I plan to re-collect the acid and put it back in my primary storage container after I soak these few pieces. I just hate to pour 2 jugs of acid in and have it eat through the plastic, thereby losing the acid and having a mess on the ground.

Thanks for any advice!

Jeff

[robertspark]

"plastic" comes in different materials HDPE, MDPE, LDPE, etc etc... some are better with some acids than others

Muriatic acid is apparently another name for hydrochloric acid https://www.thoughtco.com/what-is-muriatic-acid-608510 ..... never used it (knowingly), but I've used a lot of other chemicals for different things

a google search for "hydrochloric acid plastic compatibility"

reveals tables and sites such as these...

https://www.curbellplastics.com/Researc ... f-Plastics

https://www.plasticsintl.com/chemical-resistance-chart

http://tools.thermofisher.com/content/s ... D20480.pdf

hence its probably best to try to establish what the "plastic" actually is.

[adbuch]

I normally drop all of my cut pieces into muriatic acid for about 24 hours to clean the metal good before hitting each piece with a fine grade flap disc. I use the pans that you can buy from Lowes to put under your washing machine. It gives me a "bath" area of around 28" x 30" x 2" deep, and has worked great for me. I built a holding box out of 2 x 4s and plywood so that the trays sit in the box and have a plywood lid over them. I also keep a tarp over the whole set up when not in use and it's outside, away from any of my equipment to avoid issues with the fumes.

I have a few jobs to do that have pieces larger than what will fit into the current containers. I was contemplating building another simple frame out of 2 x 4s with a plywood bottom again but this time just line the bottom of it with sheet plastic since it will be temporary and since I can't really find large plastic pans like those used on my primary setup.

Here's the question .... Does anyone know if the acid would eat through 4 or 6 mil plastic in a 24 - 36 hour period? I plan to re-collect the acid and put it back in my primary storage container after I soak these few pieces. I just hate to pour 2 jugs of acid in and have it eat through the plastic, thereby losing the acid and having a mess on the ground.

Thanks for any advice!

Jeff

I've used muriatic acid (we put in swimming pools to balance the PH) combined with Hydrogen Peroxide for obtaining a nice "rusted" finish on some of my "yard art". I've never found the need to use it in your application. Are you using it to remove/desolve dross, or simply to etch before painting?
David

[mdwalker]

Muratic acid is great for cleaning mill scale and dross from plasma cut parts. I don't think it would eat through the plastic but you can check it yourself. Get a piece of the plastic you are considering using and put it in your current acid bath for a day or two and see what happens.

[acourtjester]

Don't know if this would help for a larger bath I bough livestock water tank from Tractor supply it holds 100 gal. I got it for the larger surface area of the parts I cut not the total volume size, The only problem was the drain plug was brass and I had to find a plastic one, found one on amazon.
https://www.tractorsupply.com/tsc/produ ... 20water%20

[beefy]

So far whatever plastic I've put my acid in has not affected it.

However, don't know if there's any particular plastic it will affect.

[Jfile]

Thank you all for the comments and advice. My usage is for soaking to remove excess dross. The top side of most pieces are usually pretty clear of dross but the bottom side definitely needs clean up. Nice long straight cuts are usually clean but short cuts and changes in direction of the torch head usually create enough build up that it needs cleaning. Soaking the piece in the acid bath for about 24 hours works wonders. Very little if any dross is left after that. I neutralize the acid with a mixture of baking soda and water and it's close to being ready for powder coating at that point.

I love the idea of the water tank from Tractor supply. Like you said, it's overkill on the depth but it would make for a really nice size for larger pieces. I think I will invest in that instead of building a temporary frame to hold a sheet of plastic that may or may not work. Acourtjester: Do you just lay plywood or something similar over the top to keep it covered?

Mdwalker: I still may take a small piece of the sheet plastic and soak it for a day or two and see what happens. Can't believe I didn't think of that before. lol

Again, thanks for the responses.

Jeff

[djreiswig]

Here's an interesting thread.
viewtopic.php?f=85&t=6471

[acourtjester]

Yes I do cover the tank when in use, here is another tank I use from Home Depot, I buy 2 sizes and the larger snuggly covers the smaller one. Having different tanks allows for small tanks for smaller parts not as much acid from the storage jug to return when finished. The only plastic I had problems with was string trimmer line I did use to separate parts but it dissolved, big mess in the acid. I now use small diameter PVC pipe for layering of parts, does not dissolve in the acid.
https://www.homedepot.com/p/Plasgad-Bla ... /205451585

[Jfile]

More great ideas and a good thread also.

I may make pictures of my set up and upload. In my opinion, it's a great set up using the pans that you typically put under washing machines. They are about 28" x 30" and about 2" deep. I have 2 side by side - one for the acid bath and the other for the neutralizer. Works great for about 90% of my projects but every now and then (like now) I have a piece that just won't fit. I think the live stock water tank is going to solve my problem. Unfortunately it just means adding another tank unless I completely do away with my current set up. I put a lot of time in it though so I hate to trash it.

Thanks!

[cstroke]

What about a shower pan? How could you seal off the hole? I havent found any that dont have the hole predrilled.

More than I'm interested in spending at the moment but....
https://www.ntotank.com/210gallon-acero ... VOEALw_wcB

[Jfile]

Cstroke,

That is definitely a nice container and would accommodate any size metal piece I would ever cut. However, as you mentioned, it's quite pricey. I think I found a temporary solution that would give me the size I need. I already use a pan similar to the shower pan, it's a pan designed to go under a washing machine to catch any leaks. It's 30" x 28" which for the most part, is large enough 90% of the time. I just had a situation where I needed to make a couple of signs that were 40" long and 20" wide which obviously wouldn't fit my normal pan. I ended up finding a pan that goes in the bottom of a dog kennel. It's approximately 52" x 35" which is an ideal size. And it's less than $40. The only problem is that it is only 1.3" deep. Obviously deep enough to submerge a piece of 14 or 16 gauge metal but very difficult to move without spilling the acid bath. I typically wouldn't have a need to move it around but at some point I would want to dump the acid and replace with fresh. I'm still trying to come up with a solution to that. If it were about 3 or 4 inches deep it would be perfect for my needs.

https://www.chewy.com/frisco-dog-crate- ... /dp/117384

Thanks for the feedback.

[DMoneyAllstar]

I've used wrapping paper totes for medium / small signs. They're like 18" by 40" and have a lid. Acid didn't do anything to the totes or lids.

I stored these outside under a lean-to roof, usually with a chunk of barn beam on top to keep wind from blowing the lid off.

Fumes will flash-rust anything in its vicinity -- do not store indoors. **And make sure kids / dogs can't knock it over, get into it, etc.**

Lastly, if you use HR P&O like me, you'll notice the residual oil start to show up in the tote. So I started scrubbing my parts with Dawn & water in a separate tub before dropping them into the muriatic acid tote.

[weldguy]

Good tip on the P&O, your acid mix will last much longer and remain much stronger cleaning the material first.