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hydrochloric acid question
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Author:  Bubbacluby [ Fri Jan 30, 2009 11:35 am ]
Post subject:  hydrochloric acid question
I know the main and active ingrediant in rust removers/converters etc is hydrochloric acid.

At the auto place it is like about $10 for 1/2 a litre up to somewhere like $20 for more.
I was at the hardware store the other day and saw they sold hydro acid for like half the price of the auto shop.

So......

Is plain hydro acid from the hardware store (about 30%) ok to use on car metal for rust removal or is there other ingredients in the "rust removers" that make it acceoptable to use on cars???

Also

Would it be ok to soak linkages and bolts etc (carby bits) in hydro acid to remove the rust then get zinc plated OR the acid will remove more than just the rust..

Thanks in advance
Brenton
Author:  awdmoke [ Fri Jan 30, 2009 11:42 am ]
Post subject: 
HCl will eat away good steel too.

It is the phosphoric acid in the rust converters that passivates & leaves the steel ready for painting. If you want to clean up rusted parts prior to plating, do a search for "caustic bath" on here. NaOH will strip the rust without eating into the good steel.
Author:  Wombat [ Fri Jan 30, 2009 12:07 pm ]
Post subject: 
Phosphoric acid - stronger the quicker it works/lasts. Hydrochloric will disolve steel and give off Hydrogen (explosive) and under some conditions Chlorine (poisonous)

Hydrochloric acid is the same (concentration may vary slightly) but the cheapest I've found is swimming pool shops
Author:  mattsmadmini [ Fri Jan 30, 2009 12:27 pm ]
Post subject: 
Wombat wrote:
Phosphoric acid - stronger the quicker it works/lasts. Hydrochloric will disolve steel and give off Hydrogen (explosive) and under some conditions Chlorine (poisonous)

Hydrochloric acid is the same (concentration may vary slightly) but the cheapest I've found is swimming pool shops


do it.... and light a match :lol:

or mix the acid with al-foil in a glass bottle with a lid on and run :lol:
Author:  david rosenthal [ Fri Jan 30, 2009 12:51 pm ]
Post subject: 
If you use hydrochloric acid dilute it to 15% ADD ACID TO WATER. The acid will dissolve the rust,but if you leave the parts in acid for days then it will dissolve any surface iron particals. The acid breaks down quickly when dissolving rust[turns to ferric chloride]
The problem with most acid cleaning is the flash rusting that occurs as soon as the parts are washed off. To aviod this remove parts from acid and immerse in solution of sodium bi-carbonate[ common baking soda] Allow parts to soak then wash off with water. I usually leave solution on parts as when it drys off it has protective coating until parts are ready for painting.
Caustic soda un-heated is very slow in removing rust, but is very good for dissolving paint and oil/grease.
On ships using heavy fuel oil we use both caustic and hydrocloric for parts cleaning because if you combine the two you end up with plain salt and water.
With ANY chemicals be very careful with what you mix together and wear proper PPE. Also read and understand the M.S.D.S that is on containers.
You can not work on minis if you have lost your eye sight. Any acid or alkaline in your eyes can permantely blind you.
Author:  mini-dunger [ Fri Jan 30, 2009 1:19 pm ]
Post subject: 
so

go to a pool shop and get some "hydrochloric acid"

Dilute it to %15

Soak parts for no longer than a day

Soak / rinse parts in bicarb and water

allow to dry with sollution or if painting straight away rinse with clean water



??
Author:  david rosenthal [ Fri Jan 30, 2009 2:24 pm ]
Post subject: 
You can buy the acid from any hardware. Only soak parts until rust is removed, the time depends on how bad the rusting is.
Just be VERY careful handling this stuff. It gives off fumes when 33% strength and can cause chemical burns.
On a side note works well when items are immersed in a barrel of this stuff.
Author:  AEG163job [ Fri Jan 30, 2009 3:53 pm ]
Post subject: 
david rosenthal wrote:
Just be VERY careful handling this stuff. It gives off fumes when 33% strength and can cause chemical burns.


That is good advice.

I believe HCl is too severe for removing rust on steel, and depending on the type of steel, the acid salts (chloride) can penetrate the metal and become impossible to remove. The result is the rust recurs even after painted etc. I even POR'd a clutch slave cylinder after using HCl and the rust still came thru.
My 2 bob's worth.
Author:  drmini in aust [ Fri Jan 30, 2009 3:59 pm ]
Post subject: 
Molasses works well on rust, and is so safe you could drink it... :wink:
No good for dirt and grease though.
Author:  Morris 1100 [ Fri Jan 30, 2009 4:26 pm ]
Post subject: 
I use hydrochloric acid every day and it is no good for rust removal. (it is not much good for hiding dead bodies either) If you wash bare unrusted metal with hydrochloric acid and then wash it off it will be covered in flash rust half an hour later.
Sure you can wash off the flash rust with hydrochloric acid again but it will still flash over before you get a chance to paint it. You still need to treat the metal after washing with acid.
Just exposing bare metal to the hydrochloric acid vapour will cause it to rust, to show you how good hydrochloric acid is, you fill a plastic bucket with hydrochloric acid the handle on the bucket will rust without even making contact with the acid.

The main ingredient in rust converter is not hydrochloric acid, it is Phosphoric acid. Just get some good quality rust converter and it will work a lot better than hydrochloric acid.
Author:  Bubbacluby [ Fri Jan 30, 2009 6:01 pm ]
Post subject: 
Ahh OOPS!!!

Sorry i got Phosphuric Acid and Hydrochloric acid mixed up. My bad
Should have checked before i posted

Makes my whole post pretty useless.

Sorry... I will check before i post next time

Thanks anyway everyone

Brenton
Author:  Morris 1100 [ Fri Jan 30, 2009 6:08 pm ]
Post subject: 
I thought that was the case but it pays to make sure. :D

I use hydrochloric acid for cleaning my concrete truck, it is great for disolving concrete off the outside of the truck.
Author:  drmini in aust [ Fri Jan 30, 2009 6:16 pm ]
Post subject: 
Morris 1100 wrote:
I thought that was the case but it pays to make sure. :D

I use hydrochloric acid for cleaning my concrete truck, it is great for disolving concrete off the outside of the truck.

That's why concrete agitator trucks are painted in 2 pack, acrylic just don't last with acid.
ps. I used to design 'em in a previous life, I helped build the first Oz automatic one with a Chrysler 245 Hemi, Torqueflite 727 autobox and Morse single lever controls... \ :wink:
Author:  Morris 1100 [ Fri Jan 30, 2009 6:25 pm ]
Post subject: 
They are usually painted with acrylic these days, if you think about it acrylic is plastic and the acid comes in plastic drums. :lol:
Acid does fade the paint but the concrete/cement/fly-ash/recycled water/etc. all fade the paint as well.

Powerpacks are a thing of the past, it is all live drives and hydraulics and cordless remote controls. The old morse cables didn't like the acid washing the grease out of them.
Author:  speedy [ Fri Jan 30, 2009 9:24 pm ]
Post subject: 
For surface rust Coca-cola does the trick without being too corrosive, leave them soaking overnight for the following results.

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