Citric acid derusting

[Kayos]

Some bits have come out nice, some need a bit more time

Also, if you use a massively strong mix because you have no idea what you are doing, you will have to smash the solid mass in the bottom of your bucket to release the small pieces embedded in it.....

 

[My Old Landy]

Can you use a fish tank heater or will the acid affect the cable/seals?

 

[Kayos]

Can you use a fish tank heater or will the acid affect the cable/seals?

I used to use an aquarium heater connected to a PID to develop colour film, was in a water bath so could do that and keep the heater separate from the acid

 

[RaceDiagnostics]

I've used aquarium heaters in other acid baths with no problems but they don't get as hot as I want for citric acid.

 

[The_Yellow_Ardvark]

I've used aquarium heaters in other acid baths with no problems but they don't get as hot as I want for citric acid.

Few years ago I did a trail with and with out heaters.

Tank one with a fish tank heater and "stat".
Tank 2, just left at room temp.
Mix was the same.

All the heat did was sped up the process of removal of the losse and surface rust. Did not seam to do much to the deep pitted and inside rust.

The cold did a better job, but only just.

I don't bother with heat now.

 

[MattF]

Just use electrolysis & save all this hassle with citric.

 

[droopsnoot]

Interesting, I've never tried citric acid at anything other than room (well, shed) temperature. At this time of year, that just means I don't use it. Electrolysis is good too, but I find results can be iffy. I do prefer it for larger pieces, though, so I don't have to mix up so much citric acid.

 

[The_Yellow_Ardvark]

Just use electrolysis & save all this hassle with citric.

That cost more ££££ and can go bang.
Ohhh, fun times.

 

[MattF]

That cost more ££££ and can go bang.
Ohhh, fun times.

More dependable though, & no risk of etching.

 

[The_Yellow_Ardvark]

More dependable though, & no risk of etching.

I use both, depends on lazy I am feeling.

 

[Kayos]

More dependable though, & no risk of etching.

A gear cassette i chucked in turned black, is that etching?

 

[The_Yellow_Ardvark]

A gear cassette i chucked in turned black, is that etching?

Black oxide, it comes off easily.

 

[AndVal]

I bought citric acid to remove mill scale but I used most of it for cooking

What is the highest water temperature that would be safe to use with citric acid?

 

[The_Yellow_Ardvark]

I bought citric acid to remove mill scale but I used most of it for cooking

What is the highest water temperature that would be safe to use with citric acid?

I have had mine to near boiling, now some is below frezzing.

 

[AndVal]

You didn't notice any irritation to the eyes from any fumes?

 

[The_Yellow_Ardvark]

You didn't notice any irritation to the eyes from any fumes?

No, as it was outside.
If cold, it sits at the far end of the play pen, not because of the fumes.
But I don't want to kick it.

 

[Kram]

Ive got lengths of 40x40 black mild steel bar (future lathe holders). This scale wont strip, heated to 70c. If I hit the scale, small peices flake off. It is clean, not oily. Any ideas?

Any ideas on this, citric is not touching it.

 

[Seadog]

Vinegar or hydrochloric acid (brick cleaner, HCl). Use the HCl with caution and don't breathe the fumes, but it will shift it very quickly.

 

[MattF]

A gear cassette i chucked in turned black, is that etching?

Nope. You get that with electrolysis too.

That photo of a bolt, further back. That type of effect, to varying degrees. That's an extreme case. May be as little as a dulled surface finish, to more notable surface degradation.

 

[Ross365]

Just use electrolysis & save all this hassle with citric.

The problem with electrolysis is that with complex shapes you don't get uniform electric field and some areas are cleaned while others not. A complex shape immersed in citric sees a uniform process over all of it's surface. I don't have any data on how temperature influences citric cleaning, but you'd certainly expect increasing temp to increase speed. Throwing in ~5% of isopropyl alcohol in to citric solution will act as a wetting agent without any adverse effects.