Hi from Natal,South Africa

[Tinus DeyselParticipant @tinusdeysel21051]

Good day everybody.I built a Simplex about 25 yrs ago and then did other things. Now the bug bit again and I am looking to build a USRA switcher in 7.25 gauge.Workshop modestly equipped but many hand tools.Will be looking for advice as I go along….

I

[Tinus DeyselParticipant @tinusdeysel21051]

[Michael GilliganParticipant @michaelgilligan61133]

Welcome, Tinus

I know nothing about either beast; but at least this will bump your post to the top, for someone to notice.

MichaelG.

[Neil WyattModerator @neilwyatt]

Hello TInus, welcome aboard the forum,

Neil

[Brian HParticipant @brianh50089]

Hello Tinus and welcome.I think many UK modellers are into railways/railroads so you should have plenty of correspondence.

Ask away, there will always be people on here to help. We also like pictures.

Brian

[Tinus DeyselParticipant @tinusdeysel21051]

Thanks for the kind welcome.I have spent the past couple of days removing mill scale and superficial rust from two 1500mm lengths of 100 by 20 mm hot rolled mild steel by hand using oldish large files.This will be the frames of the 0-8-0 loco I have started building.

[vintagengineerParticipant @vintagengineer]

Posted by Tinus Deysel on 18/12/2016 16:19:09:

Thanks for the kind welcome.I have spent the past couple of days removing mill scale and superficial rust from two 1500mm lengths of 100 by 20 mm hot rolled mild steel by hand using oldish large files.This will be the frames of the 0-8-0 loco I have started building.

An easier way to remove mill scale is to soak them in a vinegar salt bath. Take a large quatity of ordinary vinegar and dissolve salt into it till it becomes saturated. Then leave you steel soaking over night in this and all the mill scale will lift off. It is also good for removing zinc plating and galvanising!

[BazyleParticipant @bazyle]

I cannot see any way in which the salt part of that recipe is beneficial.

[vintagengineerParticipant @vintagengineer]

Its a synergistic interaction and has been used by blacksmiths for years.

[JasonBModerator @jasonb]

Quicker way to get mill scale off is to dunk the bar in brick cleaner for 1/2hr, the acid is a bit stronger than vinigar. Also dislodges tenacity flux very well. But may not be available locally.

Edited By JasonB on 18/12/2016 18:27:35

[Anonymous]

Posted by vintagengineer on 18/12/2016 18:19:03:

Its a synergistic interaction………………….

How does it work?

Andrew

[vintagengineerParticipant @vintagengineer]

When you combine two chemicals together you get a stronger reaction than each chemical on its own.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andrew Johnston on 18/12/2016 19:09:39:

Posted by vintagengineer on 18/12/2016 18:19:03:

Its a synergistic interaction………………….

How does it work?

Andrew

My guess would be that being organic, Acetic Acid is only weakly ionised. As the scale removing reaction is electrochemical, adding salt would make a better electrolyte, thus speeding the reaction up. Must be more complicated than that as salt, water and air on their own cause severe rusting. Possibly that gets behind the scale and levers it off, allowing vinegar in to finish the job.

I think the mix is worth trying. Watch this space, I'm doing some de-scaling tomorrow.

Greetings and welcome to Tinus, whose thread has been hijacked…

Dave

Edited By SillyOldDuffer on 18/12/2016 19:48:52

[Anonymous]

Thanks Dave, rather more helpful than the previous 'reply'. Although it did tell me rather a lot about the poster.

I'll be interested to see the results of your descaling experiments.

Andrew

[vintagengineerParticipant @vintagengineer]

I do apologise for posting such a complicated answer. Next time I will make sure I use very basic simple language so people can understand.

Posted by Andrew Johnston on 18/12/2016 20:41:51:

Thanks Dave, rather more helpful than the previous 'reply'. Although it did tell me rather a lot about the poster.

I'll be interested to see the results of your descaling experiments.

Andrew

[SillyOldDufferModerator @sillyoldduffer]

I happened to be making a pair of jaws for my vice when the Vinegar / Salt question was raised. As the jaws are made of Black Mild Steel, I was well placed to run a comparative trial.

I used a plastic two compartment fast-food container to hold the pickles. Each contained 75ml of Tesco Distilled Vinegar claiming 5% Acidity on the label. I dissolved 15g (a dessert spoonful) of Table Salt in the left hand compartment. I did not heat the mixture, or the metal. My garage is unheated, about 12C during the experiment.

After one hour the salted vinegar was showing signs of activity – a little bubbling, with some not very obvious reddening of the scale.

After 6 hours both jaws showed signs of reddening, but it is obvious that cold Vinegar and Vinegar+Salt are not having much effect on the scale. Vinegar+Salt is slightly more effective.

Not much difference after 22 hours immersion this morning; Vinegar+Salt is very slightly better, but it can't be seen in the photo, so I didn't post it.

At this point I turned the two jaws on edge to bring the cut edges close to the surface, the idea being that this would be aerated. The scale has been mechanically removed from the 'top', but remains at the sides. After 3 hours, both pickles caused rusting on the edge close to the air's Oxygen. Again Vinegar+Salt is slightly more effective, though the difference is marginal.

On the 'bottom' side of the jaws, no rust at all:

.The interesting thing is that neither pickle had a significant effect on the scale!  I'm starting to wonder if it really is scale, that is a layer of black iron oxide left after hot-rolling. 

Is it possible that my 'Black Mild Steel' has been treated with some other type of protective layer?  If that's true, then all bets are off when it comes to Pickling.

I may have some Patio Cleaner (Hydrochloric Acid) in the garden shed: I'll try that if I can find it.

Dave

Edited By SillyOldDuffer on 20/12/2016 13:20:08

Edited By SillyOldDuffer on 20/12/2016 13:21:18

[Anonymous]

Thanks Dave, that's very interesting. I have been using ordinary vinegar to remove mill/annealing scale; 21p a bottle from Morrisons. Ok for scale removal, I wouldn't want to use it on fish 'n' chips. It takes a good 24 hours to be effective, and then the scale just washes off under the tap, no rust. However, the vinegar rapidly loses its effectiveness.

I bought some patio cleaner that was utterly useless – no effect after 48 hours. Then I looked more closely at the items in B&Q and bought some proper brick cleaner. Much more effective, about half an hour to remove scale. And it kept working.

Andrew

[Michael Cox 1Participant @michaelcox1]

Dave, If I buy hot rolled steel from a model engineering supplier such as M-machine then I find that hydrochloric acid (brick cleaner) will rapidly remove the black oxide scale. However, on occasions, I have bought it in B&Q and the oxide scale is resistant to the acid even if immersed for some time. I suspect that the B&Q material is lacquered to prevent it rusting during transport and display in the store. May be other suppliers also have stock with some sort of protection.

Mike

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andrew Johnston on 20/12/2016 16:14:33:

…

It takes a good 24 hours to be effective, and then the scale just washes off under the tap, no rust.

…

 

Andrew

I'm glad you mentioned rinsing. I'd assumed that the scale would just dissolve leaving ready to go shiny metal. Wrong again!

I just tried running water over the jaws and the scale stayed put. It is a lot looser though. About half came off the salty jaw when I applied a toothbrush. Quite a lot brushed off the vinegar only jaw too, perhaps a third. I've put the jaws back in the bath to see how much comes off tomorrow.

Looks like salty vinegar is more effective than plain vinegar but not by much.

No sign of any Patio Cleaner here so I can't try that.

For some reason the whole house stinks of vinegar, I hope no-one thinks I'm making Heroin!

Dave

Edited By SillyOldDuffer on 20/12/2016 16:42:24

[vintagengineerParticipant @vintagengineer]

I tend to use brown malt vinegar don't know if it is stronger?

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Cox 1 on 20/12/2016 16:36:55:

…

However, on occasions, I have bought it in B&Q and the oxide scale is resistant to the acid even if immersed for some time. I suspect that the B&Q material is lacquered to prevent it rusting during transport and display in the store. May be other suppliers also have stock with some sort of protection.

Mike

I think you may be right Mike, especially as B&Q stuff is probably meant for decorative work. Such treatment may be quite common. The Wikipedia article on Mill Scale includes this sentence:

"Nowadays most steel mills can supply their produce with mill scale removed and steel coated with shop primers over which welding can be done safely."

Any steel experts able to comment? Is Black Steel always scale, or might the black colour sometimes be a preservative?

Dave

[SillyOldDufferModerator @sillyoldduffer]

Posted by vintagengineer on 20/12/2016 19:52:51:

I tend to use brown malt vinegar don't know if it is stronger?

Hi Vintage.

I only used distilled vinegar because I'm almost out of Brown Malt, which was my first choice. Anyway, according to the labels, my Brown Malt and Distilled are both 5%. I think this is the usual strength of food vinegar, but who knows?

Dave

[Tinus DeyselParticipant @tinusdeysel21051]

All quite informative and even entertaining,but in the end I persevered with mechanical means- the pieces of steel in question are five feet long and weighs around fifty pounds each(1500 by 100 by 20 millimetres)

[SillyOldDufferModerator @sillyoldduffer]

Posted by Tinus Deysel on 21/12/2016 08:55:07:

… in the end I persevered with mechanical means- the pieces of steel in question are five feet long and weighs around fifty pounds each(1500 by 100 by 20 millimetres)

An important detail Tinus, and you always have to work with what you've got!

One advantage of pickling (if you have a suitable bath and chemicals), is that it's easy unsupervised work. Mechanical removal is comparatively messy, noisy and time-consuming. Letting a cheap acid do the job is attractive if you're not in a rush, or you have to pay for the labour.

Cheers,

Dave

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