Citric acid rust removal

[marlinspike]

Right. A friend asked my OH if we could weld a repair to his car part. It was rusty so I tried it out with the citric acid mix. I used very hot water, soaked a couple of days. Cleaned it up a bit, then soaked again in a fresh solution. This was before:

This was after, though it has been cleaned up with a sanding bit on a Dremmel:

 

[marlinspike]

We realised that the part was cast iron, so we won't be welding it with our mig anyway. I think the citric acid has done ok, but still feel that Deox C does a better job - though I have only used that on steel so it's not really a like for like comparison.

The part is from an old Rover - P4 possibly - though I'm not sure what exactly it is.

 

[CompoSimmonite]

.

The part is from an old Rover - P4 possibly - though I'm not sure what exactly it is.

It's a rear shock absorber lower mount.

Paul H

 

[Rocketman]

Would a suspension part really be made out of cast iron? I would be surprised if it was.

 

[marlinspike]

Thanks for that Paul. Our friend does not use the web much, so I will have a look at finding a replacement. The guy who had the car previously had had the other one repaired, but a new part is the obvious way to go.

 

[marlinspike]

I initially thought it looked like cast iron as it was so heavy, but presumed it was steel as it was a car part. When it was cleaned up it looked more like cast iron and when I took it to my metal supplier today he confirmed it was, saying you could see the casting marks.

I know nothing about old Rovers, but was a bit surprised it had cast iron bits on it.

 

[Paul.]

Most likely a cast steel, with a turned or cold formed pin welded to it, the photo may be deceiving me but it looks very much like a welded joint down the side of the pin.

 

[marlinspike]

Does that mean we could mig weld it? One sold on eBay for £18 recently, so not that expensive to buy one, more a question of finding one. I couldn't find one listed on any of the Rover P4 parts suppliers sites.

 

[Paul.]

It should weld easy enough, stick would be my choice as its more tolerant of surface contamination, but mig should be ok.
Whether the MOT inspector will accept a welded repair to a suspension component though is another matter, mind you if the repairs invisible he'll never know, I would be more concerned about the strength of the pin, it looks well past it to me.

 

[dadangerman]

Anymore results on citric acid? I've been using deox c and it works well, but if there is a cheaper option I'm all ears, how much citric acid do you use with water?

 

[chunkolini]

Mix it in until it stops dissolving.
I reckon it is the same stuff.

 

[steviec_lj]

Mix it in until it stops dissolving.
I reckon it is the same stuff.

Add a few drops of fairy liquid as a degreaser/cleaner too. Works wonders for grubby car bits then!

 

[chunkolini]

good point there.

 

[Shox Dr]

Anymore results on citric acid? I've been using deox c and it works well, but if there is a cheaper option I'm all ears, how much citric acid do you use with water?

As Chunkolini states, they should come out dull grey, Marlinspike's must have been too weak a solution.

 

[DanielW]

I have had better results with wet sandblasting than that citric acid,small parts will benefit better because you have to dry the steel immediatly to stop the surface rust forming.

Wet sandblasted my ped frame...

 

[DanielW]

some really bad rust....sand £3 a bag plus using me pressure washer,how do you get rid of used citric acid? do just pour it down a drain?

 

[DanielW]

 

[chunkolini]

Getting rid of citric acid?
Down the drain, it is a food product.
The nice chap from the DeoxyC supplers said you can drink it.
How do you sand blast with a pressure washer?

 

[DanielW]

How do you sand blast with a pressure washer?

Kiln dried sand and an attachment gun for the washer as in the pic above,done in minutes rather than hour/s

Best piece a kit I ever bought for rust and the sand does not go everywhere as per normal sandblasting but still you need a protective mask and goggles.

 

[steviec_lj]

Before and after attached.

Less than 12hrs in a solution of citric acid and fairy liquid for degreasing.

Mix it hot for best results.

Goes straight down the drain, its not harmful at all. Wouldn't want to drink it afterwards tho Chunk!