Thread: Painting black metal

I am in the process of making a mobile base for my new table saw. The 50x50mm RHS is supplied coated in a blue finish ( I asked for black steel, and got that) , and the castor supports and welds are all coated in cold gal.

I want to do a good finish, ending up with hammertone.

Should I wire brush all the existing paintwork back to bright bare metal, then etch prime and then hammertone, or are the existing coatings suitable for spraying hammertone as is.

I would welcome all comments and advice

regards,
Jill

I have had success with:

Wipe all over with 'wax and grease remover' , 'prep-wash' or 'prepsol' and once dry painted with hammer tone paint.

G'day Jill
The blue paint on the steel is a primer. Just make sure you remove any visible bits of weld splatter, oil etc and then 2 coats of hammerfinish straight over the top. It will look good.
Over the years I used cans of the stuff.

regards
bollie7

Hammertone needs to really well shaken to mix all the little magnetized bits of metal into the paint so they can repel each other and go lumpy.

Originally Posted by blackhole

Hammertone needs to really well shaken to mix all the little magnetized bits of metal into the paint so they can repel each other and go lumpy.

ummmm, there are no magnetized bits of metal, the effect is created by an additive, often silicon based. it is actually a contaminant which gives you the effect.

Thanks for the advice everyone. It was great finding out that after a bit of a cleanup, I can hit the frame with the hammertone right away.

I appreciated the info on the blue coating too

regards,
Jill

Agree with the other posters, I've done this more times than I care to remember. Just wire brush off any welding residue, wipe down with a clean cloth and prepsol or similar then spray with the hammer-tone. The blue primer is quite stable and keys well, especially if you run a mist coat, let that flash off for about 45 seconds then apply the wet coat.

Remember though that hammer-tone paint uses silicon to get the mottled effect, if any trace of this is left in the spray gun next time you use it for "normal" paint you will get traces of fish-eye effects from it.

I keep one spray gun solely for use with hammer-tone paint and have another gun for normal spraying.

Ooops...

I have a sheet steel surfaced bench outside my shed that I use often - it has my metal working vice on it, and a grinder. I try to keep my metal work and wood work areas separate, but they share the same bench drill. I digress!

Have just finished coating this benchtop surface with hammertone.

Is it likely that if I work with my timber on it, as I sometimes do, the silicone in the hammertone will ruin the final finish of the timber?

regards,
Jill

no

Wouldn't have thought so, the reference to the silicon applies more to spray painting metal, one of the problems encountered is when you try and respray a repair area on a car that has been polished with silicon based polishes over the years - unless all traces of the silicon are removed then the respray will not be 100% successful - hence the warning about cleaning up the spray gun after hammertone.

It's for that reason I keep one of my older guns purely for hammertone and don't use it to spray with other paint.

well how did it turn out?

Be patient I have to modify the frame now because I have changed table saws, as one I ordered was no good, so a TSC-10HB is on the way from Brisbane. Should have frame completed by the weekend

Jill

Hi All
It has been twenty years or more but I recall someone in the paint industry telling me that prepsol was developed to remove silicon residue from panels prior to painting. That being the case put 1/2 litre of prepsol through the spray gun when finished to clean the gun out.

Roger

After cutting and rewelding my mobile base frame, and after cleaning with Prepsol ( not cheap, $15 /litre), I have used Wattyl Spraymate PR super Etch Grey (ColdGal ?) finish on the steel, and over the blue coat, so that it is all uniform.

Q1. Should I have done that over the blue steel finish as delivered?

Q2. What sort of drying time should I allow before coating with the hammertone finish? I have read the data sheet for cold gal here, but nowhere does it say when the final coat can be applied, either on the can or on the link above.

regards,
Jill

Jill

Rereading your initial post, you said that you are building a table saw base, presumably it will be housed in a shed or workshop, not exposed to the elements. Under that environment I would normally spray the hammertone directly over the blue primed steel. I've done this for the last 35-40 years and the results have proved to be quite durable. In fact I've used the same process for equipment I've built for outside use, such as mobile clothes lines for the boss - and these stay outside on all weather, and trolleys and such like that I use at the race track - all seem to survive quite well.

So for future reference my own opinion for what it's worth is that the answer to Q1 is, no you did not need to do that, you can just spray over the blue. The trick is, as I said, to apply a thin mist coat, let it set for about a minute and then apply the heavy top coat.

The answer to Q2 is unclear, generally over-coating exisiting paint must be done either within a predetermined time after the initial coat (depends on the paint but between 4 hours and 24 hours) while the first coat is still relatively soft, in which case the second coat "melts" into the first coat or it has to be left after the initial coat has fully hardened in which case you may want to lightly sand the first coat so there is something for the second coat to key to. I've looked up all my paperwork but can't find anything that seems relevant to the primer you've used. To be safe I'd leave it for a week then lightly sand and then recoat.

Hope this helps you.

As a side issue, in your inital post you said your requested "black steel" (I'm assuming you indicated this so you did not get gavlvanised steel) and then was suprised to get blue coated steel.

In general steel parlance for "black steel" is steel that has been hot rolled and has the mill scale still attached (hence the black). Other steel is cold rolled and ends up as "bright mild steel" (BMS) which doesn't have that mill scale. BMS is generally used in machining operations as it's size is much more even than "black steel", it has more inbuilt stresses though.

If you request black steel in solid bar, plate, round tubing or solid round then it will generally be uncoated, if you order "black" RHS (square or rectangular tube) it will generally be coated for convenience and corrosion protection, it's still "black" as in hot rolled steel though.

Rgds - Gavin