Polishing hard to get to steel

[pondman]

Morning.

I'm not sure if I'm in the right place for this thread but after too few hours sleep it all looks the same to me :-/

I've been polishing up my dragonflies with a wire brush attachment on a die grinder, this takes quite a while and at times I'd like to get it a bit brighter so I can laquer it and keep a lovely shine.

I have two questions:

1: Is there an easier way to polish steel bar other than with a wire brush so that its easier to get into the head a body? Is there an acid that can polish steel. I would not be to comfortable doing it myself but if I know it exists I can find somewhere to have it done.

2: would electro polishing work on mild steel? rusty steel? I've seen the great results on stainless and was wondering if the same could be done with mild steel.

I hope this makes sense!

Thanks in advance

 

[rtbcomp]

Moved up one level!

 

[ChrisJohnsSculpture]

Shifting the blue/black mill scale on hot rolled steel is always a problem.

One way to get rid of it is by pickling in acid, acid based brick and patio cleaner works (as it happens I'm just off to buy some now for that very purpose). But you do need to make sure that it is thoroughly rinsed off and neutralised before you finish it as any trapped in nooks and crannies will cause rampant rust.

Acid won;t polish the metal but it will shift the hard scale.

A wire brush won't get a particularly high polish. Scotchbrite mops, available in coarse, medium fine and super fine will produce a decent satin finish relatively easily and are soft enough to work well on curved and lightly textured surfaces.

Another option is that you can get quite aggressive glue-based polishing compounds for polishing mops which are quite effective at shifting rust and light scale and leave a decent satin finish. Some you use like grease based compound, others you apply glue to a stitched or hard felt mop, coat it in loose abrasive powder and allow to dry. They are excellent for things like cleaning rusty parts and tools.

Flap disks and wheels are also good for preliminary finishing and the finer ones will get a decent finish, not exactly mirror polished but free form visible scratches.

In general the amount of work required increases exponentially with the level of polish you want. eg a fine satin finish might take 5 minutes with scotchbrite mops, whereas a proper mirror polish could take 3 hours on the same part. One reason for this is that a satin finish tends to hide surface defects whereas a polished on tends to highlight them.

The problem with lacquer on bare mild steel is that as soon as it gets the smallest scratch, pinhole or scuff rust will start almost immediately and quickly travel under the lacquer.

In many ways an oil or wax finish will be more durable as it tends to self-repair to a certain extent. Of course you can always wax over the top of lacquer. Although you probably have to accept that a polished finish on mild steel is either going to be temporary or quite maintenance intensive.

I've not used electro-polishing myself but my understanding is that it needs to start with a decent surface finish ie clean, scratch-free bare metal.

 

[pondman]

Shifting the blue/black mill scale on hot rolled steel is always a problem.

One way to get rid of it is by pickling in acid, acid based brick and patio cleaner works (as it happens I'm just off to buy some now for that very purpose). But you do need to make sure that it is thoroughly rinsed off and neutralised before you finish it as any trapped in nooks and crannies will cause rampant rust.

Acid won;t polish the metal but it will shift the hard scale.

A wire brush won't get a particularly high polish. Scotchbrite mops, available in coarse, medium fine and super fine will produce a decent satin finish relatively easily and are soft enough to work well on curved and lightly textured surfaces.

Another option is that you can get quite aggressive glue-based polishing compounds for polishing mops which are quite effective at shifting rust and light scale and leave a decent satin finish. Some you use like grease based compound, others you apply glue to a stitched or hard felt mop, coat it in loose abrasive powder and allow to dry. They are excellent for things like cleaning rusty parts and tools.

Flap disks and wheels are also good for preliminary finishing and the finer ones will get a decent finish, not exactly mirror polished but free form visible scratches.

In general the amount of work required increases exponentially with the level of polish you want. eg a fine satin finish might take 5 minutes with scotchbrite mops, whereas a proper mirror polish could take 3 hours on the same part. One reason for this is that a satin finish tends to hide surface defects whereas a polished on tends to highlight them.

The problem with lacquer on bare mild steel is that as soon as it gets the smallest scratch, pinhole or scuff rust will start almost immediately and quickly travel under the lacquer.

In many ways an oil or wax finish will be more durable as it tends to self-repair to a certain extent. Of course you can always wax over the top of lacquer. Although you probably have to accept that a polished finish on mild steel is either going to be temporary or quite maintenance intensive.

I've not used electro-polishing myself but my understanding is that it needs to start with a decent surface finish ie clean, scratch-free bare metal.

Thank you very much, thats very helpful!! How do you wax a sculpture thats made of 8mm bar? Its very difficult to get into the parts. I think I've made my life a bit difficult making them this way.

I thought that would be the case with electro polishing.

Thanks for the great advise.

 

[outofthefire]

Thank you very much, thats very helpful!! How do you wax a sculpture thats made of 8mm bar? Its very difficult to get into the parts. I think I've made my life a bit difficult making them this way.

I thought that would be the case with electro polishing.

Thanks for the great advise.

Dead easy heat it up and rub it with a candle then buff it with a cloth once its cooled. Small bits I just stick in the oven while our lass is cooking. I've tried all sorts of different waxes including birthday cake candles and i've come to the conclusion that it doesn't matter what you use I just use the cheapest candles I can find.

 

[Terrapin]

Have you thought of blast media? Take the scale off with an aluminium grit an then blast with crushed walnut shells - we use these to decoke the cylinder heads on Washega engines without removing the heads (force valves open and blast through spark plug fitting through to manifold ports.
There are dozens of types of blast media available - talk to the suppliers to see what best fits your choice of finish.

Quick and easy once you have the initial kit set up

 

[Paul G]

I made a hammer a few weeks ago from a bit of railway line. (manganese steel)

As it's for use on aluminium I need a polished face so after turning the heads and welding them on I polished them on a stitched rag wheel,
first with grey (carborundum) soap and finished off with brown. (rouge)

Paul G

 

[pondman]

Have you thought of blast media? Take the scale off with an aluminium grit an then blast with crushed walnut shells - we use these to decoke the cylinder heads on Washega engines without removing the heads (force valves open and blast through spark plug fitting through to manifold ports.
There are dozens of types of blast media available - talk to the suppliers to see what best fits your choice of finish.

Quick and easy once you have the initial kit set up

I thought of blasting but thought it might be to aggressive, I have them shot blast if they are powder coated and its just a bit rough, I didn't know there are softer materials that can be used. I was thinking about setting up a blast room here. I'll look into it, thanks!

 

[chunkolini]

Be careful around blasting, I had my chameleon bead blasted.

It came back with a horrid surface texture as though it had been painted with silver paint.
It cleaned up a treat when gone over with a wire brush on a bench grinder.
these complex welded structures are indeed a pain to clean.

I have tried using Bilt Hamber DeoxyC as a soak to clean welded structures and it does a great job of getting rid of the welding oxides etc, still needs a quick going over with the bench grinder brush. I reckon the deoxy stuff is just citric acid so I will buy a pot of that over the internet when I next need some.

These days I make things as a series of sub assemblies, get each one clean, then build them up and just have to clean up the last welds holding it together.
This does involve a bit of planning ahead but gets a good job done.

A great final finish is Jade Oil, it penetrates and coats a treat and is not as agressive a finish as lacquer.

 

[brightspark]

bead blasting will leave steel with a satin chrome type finish but will polish up easily

 

[Shox Dr]

I made a hammer a few weeks ago from a bit of railway line. (manganese steel)

As it's for use on aluminium I need a polished face so after turning the heads and welding them on I polished them on a stitched rag wheel,
first with grey (carborundum) soap and finished off with brown. (rouge)

Paul G

Come on that deserves it's own thread fella

 

[pondman]

Be careful around blasting, I had my chameleon bead blasted.
View attachment 29821
It came back with a horrid surface texture as though it had been painted with silver paint.
It cleaned up a treat when gone over with a wire brush on a bench grinder.
these complex welded structures are indeed a pain to clean.

I have tried using Bilt Hamber DeoxyC as a soak to clean welded structures and it does a great job of getting rid of the welding oxides etc, still needs a quick going over with the bench grinder brush. I reckon the deoxy stuff is just citric acid so I will buy a pot of that over the internet when I next need some.

These days I make things as a series of sub assemblies, get each one clean, then build them up and just have to clean up the last welds holding it together.
This does involve a bit of planning ahead but gets a good job done.

A great final finish is Jade Oil, it penetrates and coats a treat and is not as agressive a finish as lacquer.

Thanks Chunko

There seem to be many possibilities I think the sub assembling idea will work well for me, I used to do it with my men so not sure why I didn't think of that! I love this forum, so many helpful people! I've never heard of jade oil so I'll look it up.

 

[pondman]

Come on that deserves it's own thread fella

I was thinking that myself! Thats an awesome hammer right there!!

 

[Terrapin]

On the blast cleaning / polishing front. If you go to someone who runs a professional blast service (not Mr I sandblast walls etc.) they should be able to demonstrate different finishes for you. On the 'soft' blasting media front you can use bicarb powder and we also use dry ice - leaves no residue as it gases off - just ensure you don't use in a confined space without breathing gear. I think in your line of work your own blast room/cabinet would be an excellent addition.
Here's a drinks can - soda blasted on one side - no distortion , nice finish

 

[chunkolini]

Jade Oil http://www.jpennyltd.co.uk/shopping/pgm-more_information.php?id=27
I may have to try some of their cold patination stuff as well.

 

[rtbcomp]

Have you tried blasting an empty can, ie one where there is no internal pressure keeping the walls straight?

 

[MattF]

I thought soda blasting was supposed to not damage the metal layer in any way? It looks like there is notable pitting on that cans exposed surface.

 

[brightspark]

Have you tried blasting an empty can, ie one where there is no internal pressure keeping the walls straight?

exactly that can is pressurised. ive just blasted an empty can at low pressure with a suction gun using that fine yellow media and it ruined it

 

[pondman]

So I went to my painters with this problem and asked if they had soft media blast, They didn't but they told me about a job that they did where they basted the steel then heated it up till it changed colour. So I did this and am very pleased with the results!!

Thanks for all the advice!!

 

[Premiershipman]

What did you use to baste the metal in ?