Thread: Strength of phosphoric acid?

Hi All,
Hey, what is wrong with a bit of Vinegar & a bit of Steel wool to get that rust off.
A dash sight cheaper than $35.
Yes, I've used Coro Dip, & yes, it worked fine, BUT, so does Vinegar.
I use 8 to 1, being 8 of water to 1 of Vinegar & leave in a Plastic Container.
I leave mine outside & cover it with a bit of Plywood to help stop Evaporation.
I suppose I'm lucky, that I'm allowed to clean my rusty bits in the Laundry Sink. I use a fair bit of Washing Powder, in hot water,& use a Brass Brush to wash all the rubbish off, then run it under the Hot Tap & dry with an old towel.

Originally Posted by issatree

I suppose I'm lucky, that I'm allowed to clean my rusty bits in the Laundry Sink. I use a fair bit of Washing Powder, in hot water,& use a Brass Brush to wash all the rubbish off, then run it under the Hot Tap & dry with an old towel.

Awww ... memories ... that's how my old mum used to wash me when I was little



Paul McGee

Originally Posted by pmcgee

Awww ... memories ... that's how my old mum used to wash me when I was little



Paul McGee

Did she use vinegar and steel wool too?

Hi all,
Well you may laugh, Ha, Ha, but My Mum did use Vinegar on us when we were silly enough to get Sunburnt . It really took the soreness out of the burn.

So what were the words of wisdom about using Vinegar & Water on Rusty bits.

Originally Posted by issatree

So what were the words of wisdom about using Vinegar & Water on Rusty bits.

As I understand it, phosphoric acid reacts with rust to form an inert substance. Vinegar reacts with olive oil to form salad dressing.

Originally Posted by jack620

As I understand it, phosphoric acid reacts with rust to form an inert substance. Vinegar reacts with olive oil to form salad dressing.

Yes that's correct Chris. I can't recall the compound that's formed, but it basically protects the steel. I haven't tried vinegar, but I've tried several other acids and the part will literally rust before your eyes once it's removed from them. I use phosphoric acid before painting if there's light rust, any heavy rust I drag out the big-guns and just wipe it down the light rust that forms with phosphoric just before painting/powder coating

Pete

So says Wiki

"The phosphoric acid converts reddish-brown iron(III) oxide, Fe2O3 (rust) to black ferric phosphate, FePO4.
"Rust converter" is sometimes a greenish liquid suitable for dipping (in the same sort of acid bath as is used for pickling metal), but it is more often formulated as a gel, commonly called naval jelly. It is sometimes sold under other names, such as "rust remover" or "rust killer". As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces.
After treatment, the black ferric-phosphate coating can be scrubbed off, leaving a fresh metal surface. Multiple applications of phosphoric acid may be required to remove all rust. The black phosphate coating can also be left in place, where it will provide moderate further corrosion resistance (such protection is also provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes)."

Hi Jack620,
As It says, put it into English, as I'm not sure what you mean.
I have a few Tools in the V/W at this time, & when I get to clean them up, I expect for them to be a Beautiful Light Grey in colour.
To stop the future rust, most of my stuff is in Wooden Draws with an old Tea Towel that was soaked in that Product that those Shoe Shiners try to sell you, which is most likely Lanolin.
No Rust in My Shed.

Originally Posted by jack620

As I understand it, phosphoric acid reacts with rust to form an inert substance. Vinegar reacts with olive oil to form salad dressing.

Hi Issatree,
sorry if I sounded flippant. I was just making the point that phosphoric acid and vinegar both have their specific uses. Pete F and Stu filled in with the details. It's the compound that phosphoric acid converts rust into that makes it suitable for the job. Vinegar doesn't convert rust, so is less suitable for the job. It may well remove rust (I haven't tried it), but it doesn't convert it to an inert compound.
Cheers

Originally Posted by issatree

Hi All,
Hey, what is wrong with a bit of Vinegar & a bit of Steel wool to get that rust off.
A dash sight cheaper than $35.
Yes, I've used Coro Dip, & yes, it worked fine, BUT, so does Vinegar.
I use 8 to 1, being 8 of water to 1 of Vinegar & leave in a Plastic Container.
I leave mine outside & cover it with a bit of Plywood to help stop Evaporation.
I suppose I'm lucky, that I'm allowed to clean my rusty bits in the Laundry Sink. I use a fair bit of Washing Powder, in hot water,& use a Brass Brush to wash all the rubbish off, then run it under the Hot Tap & dry with an old towel.

All acids will remove rust but as stated phosphoric converts to an inert compound. Vinegar in the bottle is a solution of about 4% acetic acid so is already very dilute. I use it to clean dirty stainless kettles. Pour in about a cup full, top with water, boil. Rinse, repeat if needed.

We use 85% phosphoric at work to neutralize caustic and as a cleaning step when cleaning our centrifuges. We buy in 200l drums. When the drum is empty (almost) there is enough left for me to take home. We use a pump to empty the drum into a bucket but the pump does not get it all. Due to the danger we are not supposed to use any other method. It is much safer at home tho!

I agree that it should be diluted to about 35% or so. I have used conc acid before and had to add water to get it to remove rust. The water is needed to create H3O+ ions which do the work. I would suggest that the acid is washed off with water after use. Then wipe etc dry.

Dean

Just remember to add acid to water and not the other way around.

Originally Posted by barney2804

Just remember to add acid to water and not the other way around.

Thanks for that timely reminder. I was going to mention it but I forgot.

Dean