Phosphoric acid
 

I'm looking for a better way to remove rust on steel tubes(raw stock) at work so we got a bottle of phosphoric acid(presumably diluted).

A co worker asked if the steel needed rinsed or if the acid would continue to eat the metal. I assumed once wiped off the acid residue would evaporate and cease to etch or eat the metal. Can someone confirm this?

I don't know what I'm talking about but wouldn't it have to be neutralized and not just wiped clean for the acid to be completely gone?

This is what google had to say. Could vary by product but I would assume its the same.

http://www.kleanstrip.com/product/phosphoric-prep-etch

Some people that have experience using the stuff here.

http://www.practicalmachinist.com/vb...ersion-225471/

Neither of those tell me what I want to know though. Pretty much I'm looking for: can I wipe it(liquid acid sprayed on) off with a dry towel and walk away or will the remaining acid residue on the steel continue to eat the material?

Excellent reviews on this stuff

http://www.evapo-rust.com/

Says it"contains no acids"

From what I have read it is a rust converter. It will not effect bare metal other then to give it rust protection. It does say however you need to make sure it has fully run its course before getting it wet or the combination of water with the acid will cause white powder spots. So long story short from the few forums I've read on its use just wiping it down with water is fine once its done to remove all the loose rust it has converted.

To give you an actual answer, Phosphoric acid is fairly strong, but nothing like Hydrochloric (Muriatic) acid or Sulfuric acid. Will it continue to eat the metal after you wipe it off? Depends on how strong the concentration is, but if you can wipe it down with a towel and not have the towel dissolve in your hand, then it should be fine.

Also depends on how long its going to be sitting, because the acid will act on the metal over time, but probably not enough to cause any kind of structural problems. Rinsing/diluting is the safest way, but make sure you towel off the metal afterwards or you will just end up with rust again.

Fun fact, phosphoric acid is used in Coca-cola, and can be used as a chrome polish along with aluminum foil (Thanks Mythbusters!)

Safety Fact: Always ADD ACID to water, not water to acid when diluting. Rinsing in this case would be ok, but if you have acid you need to dilute, always add it to water to prevent any adverse reaction.

https://media1.giphy.com/media/Y2nbrJyAR6RiM/200_s.gif