The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Stu55Flash on 26.10. 2010 18:09

Title: Removing Exhuast Bluing
Post by: Stu55Flash on 26.10. 2010 18:09
Having blued my headers with too rich a mixture I need to remove the blue from the chrome work. Question is what's the best way of doing this? Has someone got a secrete recipe - like cheap way of doing this?

Regards

Stuart
 
Title: Re: Removing Exhuast Bluing
Post by: bsa-bill on 26.10. 2010 18:31
I'm very sceptical about products that claim to remove blue, where is the blue? - I think it has to be in the nickel which is under the chrome, so to remove the blue you will need to remove the chrome, I would be very happy to be convinced otherwise as it would be a boon to keeping the bike nice although lots of folks like their pipes blue.
As ever I'm happy to be taught differently so come on all our metallurgists enquiring minds need to know

Stuart I always thought Bluing was a result of overheating which would indicate a weak mixture or too retarded ignition.

All the best - Bill

Title: Re: Removing Exhuast Bluing
Post by: Stu55Flash on 26.10. 2010 19:54
Quite right Bill. I meant too weak.

Since posting I tried some Kleenze stainless cleaner - says none abrasive on the container. It met my criteria of being cheap as she already had some under the sink. Its done something: the blue has sort of gone but the chrome is sort of grey. From what I've read the blue comes from oxidisation at the surface. So it can be removed by rubbing off the surface chrome but this is not a good idea for obvious reasons.

Stu
Title: Re: Removing Exhuast Bluing
Post by: cus on 26.10. 2010 23:13
G'day Guys,
My A10 doesn't blue the pipes, it runs more on the rich side, but my bonnie used to. I had some success with keeping it at bay
by using Prepsol (wax & grease remover), sounds strange, but give it a try! Soak a rag in prepsol, give the area a rub, then leave
a good coating on it to evaporate off. It doesn't completely remove it, but takes it back to the original blueing that took place.

regards, Cus
Title: Re: Removing Exhuast Bluing
Post by: Retired Fireman on 27.10. 2010 03:43
Hi guys, the only product I have found any good for getting the blue off is a polish called in OZZ " Autosol Metal Polish Liquid" not to be confused with the paste in a tube we use for alloy, I use this every time I come back from a long run and it takes a bit of time but works reasonably well if applide thick and left for a beer or 2 then just have another 2 beers while you polish!  You can get it at repco and Supercheap.
Title: Re: Removing Exhuast Bluing
Post by: BSA_54A10 on 27.10. 2010 07:59
Stainless pot cleaned is acid.
You pipes look dull because they are now full of tiny etch pits.
Your best hope of recovery is a mechanical polish.
Try Silvro , which is very fine, at 0 micron to 2 micron.
If after 15 minutes you seem to be going no where then up one grade to Brasso 2 to 4 micron
If no joy there then try some chrome wheel polish 6 to 10 micron.

If you really want to remove blueing chemically then you need to use cyanide on a hot pipe
Some hot iron cleaners used to contain some cyanide type reagents so that might work. 
Title: Re: Removing Exhuast Bluing
Post by: Triton Thrasher on 27.10. 2010 09:37
cyanide on a hot pipe


Give me shiny pipes or give me death!
Title: Re: Removing Exhuast Bluing
Post by: Retired Fireman on 27.10. 2010 10:45
When I TIG weld stainless steel I remove the "burned weld look" with S/S pickling paste, I think this stuff is pickric acid. It completly restores the burnt look around the welded stainless to perfect shiny S/Steel after a little time and a scrub with a stainless wire brush then rinse off with water. It is pretty deadly stuff with all sorts of warnings about what it does to your health if you get it on you but tomorrow morning I might try it on an old set of pipes I have in the workshop and report back what happens you never know to you try.
Title: Re: Removing Exhuast Bluing
Post by: bonny on 27.10. 2010 12:09
When I TIG weld stainless steel I remove the "burned weld look" with S/S pickling paste, I think this stuff is pickric acid. It completly restores the burnt look around the welded stainless to perfect shiny S/Steel after a little time and a scrub with a stainless wire brush then rinse off with water. It is pretty deadly stuff with all sorts of warnings about what it does to your health if you get it on you but tomorrow morning I might try it on an old set of pipes I have in the workshop and report back what happens you never know to you try.

that pickling paste is lethal to non-stainless steels though retired fireman , i was in a rush one friday evening to get home from the engineering shop i worked in at the time and left the top off a big tub of pickling paste, when i came in on  monday everything in the whole place that could rust did rust and fairly badly and even worse the closer they were to the open tub, it also turns your skin yellow .
Title: Re: Removing Exhuast Bluing
Post by: MG on 27.10. 2010 14:02
Caswell sells this stuff, haven't tried it myself though, so no idea whether it works:

http://www.caswellplating.com/buffs/bluejob.html (http://www.caswellplating.com/buffs/bluejob.html)


Since non-ferrous metallurgy is not one of my strong points, can anyone (like Trev for instance *wave*) explain what the mechanism behind ex pipe blueing is?
Is it simply an annealing colour like with steels? Or surface oxidation of the chrome? Or something completely different?

I'm having the chrome-pipe-blues.  *whistle* *sad*

Cheers, Markus
Title: Re: Removing Exhuast Bluing
Post by: orabanda on 27.10. 2010 15:06
A tip I got from an old car restorer, was to spray the inside of chromed pipes (at the hottest part - the header) with a heat resistant paint.

I have tried this with some success; works two times out of three.
Title: Re: Removing Exhuast Bluing
Post by: BSA_54A10 on 28.10. 2010 00:04
Pickric acid is an extremely dangerous chemical.
If allowed to dry it forms a highly meta stable crystal which will explode with very little mechanical prompting.

Picric acid dissolved in methanol is the standard trigger for letter bombs.
You use it to wet the glue and the mechanical force of the person opening it will cause it to explode and this is used to ignite the main explosive.

And yes it is used primarily for etching stainless steel.
We used to submerge the bottle of Picral in warm water till the stopper was wet through before opening the jars.
It has been responsible for removing more fingers than any other chemical commercially used.
Twist the stopper with some dried crystals around the lip and bye bye fingers.

I would imagine that the pickleing paste would only be 3 % to 5 % pickric acis.
If you use this stuff, do not open an old jar / tube unless it has been wetted down first and thoroughly clean the top before it is replaced.

OTOH one of our "fun" tricks was to paint the steel stairs with a 0.1% Picral solution on hot nights.
When the foreman came up in his furnace boots ( steel plates in the sole ) it would explode beneath his feet
Title: Re: Removing Exhuast Bluing
Post by: BSA_54A10 on 28.10. 2010 00:30
Yes Markus the blueing is exactly the same thing.
Not sure if it is the chrome or the iron oxide growing through the micro cracks in the chrome.
Never seen chrome in any other form than pellets ( for plating) or notched sticks ( for alloying ).
The standard chrome (II I think) oxide formed at room temperature is light grey and not porus which is the only reason why stainless dose not rust very well as it forms an air tight non conductive layer over the iron.
At elevated temperatures all metal oxides will physically & chemically combine, it is just a matter of how high a temperature this happens.
This is exactly what vitrious enamel is, metal oxides fused with a colour pigment ( usually another metal oxide) at high temperature.
Some of you probably did this in art class at school with copper ( usually pennies ) enameled with metal oxides many of which changed colours after being baked. That which dropped off & fell to the floor of the oven just formed beads and did not combine as it needs the free electrons from the base metal to change phase.

All metals have several different oxide colours which may or may not be stable at room temperature but all of which are temperature dependent during formation. It is part & parcel of the "metallic bond" . Second thing that you look for when examining a failure.
Title: Re: Removing Exhuast Bluing
Post by: Retired Fireman on 30.10. 2010 12:13
Now I remember where I encoutered Picric Acid, It was in Afganistan in 2001 during my terrorist training course!!
Title: Re: Removing Exhuast Bluing
Post by: Topdad on 08.06. 2011 16:04
i've got the caswell kit ,spoke to guy who makes all there products ,very helpful, I've only used it once and not as per the length suggested by instructions but it was working and pref to blowing yourself/bike up or trying to explain to "she who must be obeyed " as to how you went out white and came back yellow! You get the stuff in bottle and a special mop which fits round pipe and use an electric drill to attack the pipes, worth what it cost, regards Bob.