15 replies to this topic

[skoughi]

So I'm going to admit to being a numpty! I've been having a go at the vinegar bucket on rusty parts with success, until tonight! I've been throwing in various parts and leaving them for a week then giving them a good scrub then a going over with water to wash off any remaining vinegar. All good. I sripped the rusty pistons and old seals from the calipers and seeing as they were in a right state then they got thrown in as well, mistake! After at least a week for one and probably nearly two for the other. The first one is perfect, looks like new and has received a coat of primer tonight. However the other has been eaten alive! A lot of the surface has crumbled off and left it like an old iron bar thats been in the sea. Is this a case of don't put certain metals in vinegar or put anything in vinegar but only for a certain time or do I have a poor quality caliper. I'm now on the lookout for a drivers side caliper!

[sledgehammer]

sounds like it was very rusty ?

 

normal vinegar only eats rust  - won't touch clean steel - 

 

I wonder if vinegar left in a damp environment will absorb water ?

 

it will certainly get weak the more it is used

 

once taken out of vinegar , rinse with water & dry very quickly - it will rust rapidly until treated in some way like wd40 , paint etc

 

also I have found - if wire brushing something , dab some vinegar on first , give it a min , then wire brush off

 

- the rust comes off quicker

Edited by sledgehammer, 23 October 2013 - 09:22 PM.

[SecretSugar]

Safe to say keep your vinegar for your fish and chips 

[jaydee]

You left it too much in vinegar, probably the acid has gone and the water rusted the steel

[skoughi]

Its still working quite well, it was a very strong mix I made. I was very surprised at how the surface of the caliper simply scraped off. I went over it with a wire brush in the die grinder and what was left looked like wrought iron, whereas the other one looks like new. Everything else has come out quite well. I've been giving parts a good wash then dry in front of the space heater. After that its a good going over with jenolite and wire wool and etch primer. Lot less noisy then the blasting cabinet and I don't have a compressor going at the whole time!

[dklawson]

Different acids can be used to remove rust.  With all of them, time of exposure can be critical.  I have seen that steel and iron parts with higher carbon content (such as case hardened parts) are more aggressively attacked by acid... leaving them with a rough, pitted surface if left unattended too long.  It could be that your damaged caliper had higher carbon than the one that was less affected.

 

WIth a caliper there are two areas to really be concerned with, the piston bore seal glands and the bleed nipple seats.  If the other surfaces are rough and pitted it doesn't matter quite as much.  (If you split the caliper you also have to worry about the tapped holes and the sealing washer surface between the two halves).  The seal glands in the piston bores must have good, sound walls for the square cut rubber seals to seat against.  The piston bores themselves can have some pitting as no sealing takes place on those walls.  However, big/massive pitting of the bores would be a problem as there will be less support surface for the piston itself.  It should go without saying that severe etching of the bleed nipple seat would be a problem as you could never get it to seal.  If your damage was not in the sealing areas, multiple applications of primer followed by sanding and top coat painting should leave the caliper in presentable and serviceable condition.

 

Regardless, it is important to frequently monitor what is going on with parts soaked in acid.  So the parts all behave the same (or close to the same) it is best to thoroughly degrease them carefully and well and put groups of similar parts in the acid bath at the same time.  Check them frequently and remove them at the first sign that a critical surface is being adversely affected.

[JustSteve]

I posted this before...      I saw a topic showing how to use vinegar to remove rust from brake cylinders... so i tried it.

 

 

The general census was that I was a t**t    Still have loads of vinegar left in the shed 

[Tamworthbay]

Not as cheap,but bilthambers DEOX C works in the same way. It is safe to leave as long as you want (usually overnight is enough) and coats the metal ready for primer.

[bpirie1000]

Are you not supposed to soak in bicarbonate of soda to neutralise the acids...

But yer right about time leaving it in acid for...
Used this on an old bike bottom bracket years ago... Worked a treat...

[dklawson]

Rinsing with bicarbonate dissolved in water should neutralize the acid and certainly won't hurt.  However, rinsing with clean water followed by wiping and drying the surface should suffice also. 

[skoughi]

Here is a picture of the two calipers that I soaked in vinegar. You can easily see how its effected the surface of the metal. This one is now for the bin as the edge of metal that holds in the outer piston seal has been eaten away so I don't think it'll be safe to use. I'm on the lookout for a new drivers caliper now!

 

 DSC_0250 (2).jpg   125.45K   34 downloads

[pothole]

Could it have been that in the past one of the calipers was replaced with a new one therefore when soaked in vinegar the older one looks worse.

[skoughi]

Yeah I think you're probably right, I remember thinking it looked a bit rough before it went in the vinegar and it did seem to have some sort of paint on it which was probably hiding the rough finish. The cost of a new or good second hand one means its not worth trying to make it serviceable. I've done the other with some jenolite, etch primer, primer and some rattle can alloy wheel paint and I don't mind admitting that it looks quite nice!

[jaydee]

My fav choice is phosphoric acid, about 30% acid 70% water, works a treat

[dklawson]

My fav choice is phosphoric acid, about 30% acid 70% water, works a treat

 

That is also what I use.  I buy a gallon of it pre-mixed from a local agricultural supply house as needed.