citric acid de-rusting (again!)

[bigegg]

just found this:

https://chemistry.stackexchange.com...icvinegar-and-citric-acid-as-the-rust-remover

suggests adding table salt to citric acid.
*apparently* it makes the citric acid convert the rust to ferric chloride, rather than ferric citrate.
ferric chloride being more soluble in water, so less of protective film develops on the item, meaning less cleaning, and faster de-rusting.

going to give it a try...

 

[RaceDiagnostics]

Great tip, I did some derusting with citric acid last week and had a strange affect, it seemed like there was a copper coating left on the steel which I had to wire brush off. I wonder if the copper came off of my heating element.

Before.

During.

After, unfortunately did not take a picture with the copper like coating, but you can see it a bit in the pitted areas.

 

[DennisCA]

Good if it works, I just ordered 5 kilos of citric acid.

 

[RaceDiagnostics]

I normally scrub the parts every hour or so, and sometimes there are stubborn areas I get into with a pick, hopefully the salt will help with this.

 

[Shox Dr]

I noticed a copper like film on derusted parts awhile back. Still don’t know what is was

 

[steveo3002]

how much are you planning to add? got some parts i want to try for the first time waiting in the shed

 

[RaceDiagnostics]

I will start with a handful of salt to a bucket of water.

 

[bigegg]

how much are you planning to add? got some parts i want to try for the first time waiting in the shed

im going to add 10g of salt to 100g of citric acid powder, then add to 2l of water at ambient temp, which about 10-15c at the moment.

<edit> or you could just put a handful in a bucket

 

[RaceDiagnostics]

It works much better when hot, do you have any way to heat it.

 

[steveo3002]

seen some folk take out a jug at a time and microwave it ?

 

[The_Yellow_Ardvark]

Use dishwasher salt.
So much cheaper.

To heat mine I use hot water from a tea urn as a base.

Then using a "salvaged" heater from a hand wash to keep it at a high temp.

The fixing of that is a bit "Heath Robinson" and would have @Parm blowing steam. But it is safe.

Try to keep the parts off the bottom of the container, as this will allow the solution to circulate.

I mix mine to start, 1 table spoon of acid to 1lt of water, then add more until you see a reaction and it will take on a acid smell.

As for the salt 1/2 table spoon per gallon. You don't need a saturation of the salt just a base level

 

[Seadog]

I wonder if the copper came off of my heating element.

You've got a rudimentary battery with an acid and two dissimilar metals. The copper was coming from your heater and depositing on the steel. If you have a copper sulphate solution it will readily plate clean steel just by dipping it in. It was often used for marking out, we certainly did it that way at school in the 1960s.

 

[MattF]

If you have a copper sulphate solution it will readily plate clean steel just by dipping it in. It was often used for marking out, we certainly did it that way at school in the 1960s.

That's something I've been wondering. Does it need to be sulphuric acid, or will milder acids work for that solution?

 

[Shox Dr]

You've got a rudimentary battery with an acid and two dissimilar metals. The copper was coming from your heater and depositing on the steel. If you have a copper sulphate solution it will readily plate clean steel just by dipping it in. It was often used for marking out, we certainly did it that way at school in the 1960s.

May well have done, not sure where it came from when I saw it. Stainless parts in a stainless ultrasonic cleaner, no copper in sight

 

[Seadog]

Apparently:

"Copper (Cu): Copper is normally present in stainless steel as a residual element. However, it is added to a few alloys to produce precipitation hardening properties or to enhance corrosion resistance particularly in sea water environments and sulphuric acid."

 

[Cobbler]

It was often used for marking out, we certainly did it that way at school in the 1960s.

That takes me back, Seadog. I’d forgotten all about that. Copper it & mark with a scriber

 

[TechnicAl]

just found this:

https://chemistry.stackexchange.com...icvinegar-and-citric-acid-as-the-rust-remover

suggests adding table salt to citric acid.
*apparently* it makes the citric acid convert the rust to ferric chloride, rather than ferric citrate.
ferric chloride being more soluble in water, so less of protective film develops on the item, meaning less cleaning, and faster de-rusting.

going to give it a try...

The salt will also produce some HCl with the H in Citric.....HCl is hydrochloric acid

 

[bigegg]

May well have done, not sure where it came from when I saw it. Stainless parts in a stainless ultrasonic cleaner, no copper in sight

ive just pulled an old tinned(?) cake tin out of the bath.
cetain bits of it, at first glance, look coppery but its actually a rust?burnt on oil?
is it possible thats whats on the parts?

got to ask though - why would you be de-rusting stainless?

 

[Shox Dr]

ive just pulled an old tinned(?) cake tin out of the bath.
cetain bits of it, at first glance, look coppery but its actually a rust?burnt on oil?
is it possible thats whats on the parts?

got to ask though - why would you be de-rusting stainless?

They were brake dis s off one of my bikes, just needed the crud cleaning off them. Came out with a slight copper tint in places.

Thinking about it, there would have been copper in the pads?

 

[The_Yellow_Ardvark]

Mine on the go.
Citric acid, dish washer salt and the "Hmm" heater removed. It was sat at 45deg C.