Painting black metal

[Dengue]

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

[blackhole]

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.

[bollie7]

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

[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.

[yozza]

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.

[Dengue]

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

[Gavin Newman]

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.

[Dengue]

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

[echnidna]

no

[Gavin Newman]

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.

[bobsreturn2003]

well how did it turn out?

[Dengue]

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

[rogerbaker]

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

[Dengue]

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 (http://www.firequip.com.au/files/Technical%20Data%20Sheets/General%20Supplies/HiChem%20Cold%20Gal.pdf), but nowhere does it say when the final coat can be applied, either on the can or on the link above.

regards,
Jill

[Gavin Newman]

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

[Dengue]

Hi Gavin, many thanks for taking the time to do this excellent response. I have certainly learnt a lot from this thread, and will know what to do next time.

I will now let it cure, as you indicate, and spray the final coat next weekend.

regards,
Jill

[bollie7]

Hey Jill
Obviously you take pride on your work which is great to see. You will find with the hammer finish that it is very very forgiving of the person applying it. Where I work its nicknamed "Fitters friend" because it can make the dodgiest fabrication job look good.
With the amount of care you have put into this job I think you will be very pleased with the results.

don't forget to post some pics when finished.

regards
bollie7

[durwood]

As mentioned in previous threads just wipe over the metal /blue primer with a solvent to make sure that the surtface is clean.

Hammerfinish is just enamel with silicone added, the silicone not only helps in the protection of the object (its great at repelling moisture but it tends to repel paint. if present one of the reasons its in some polishes)

As someone mentioned it is a big problem on cars if silicone is on it. If you spray over a surface when it is on there the new paint beads up and you get the Fish Eye or hammer effect ( hammer because it looks like it has been tapped with a ball pein hammer)

Hammer finish has been around for many years it is usually applied to steel direct as a quick and tough finish on such things as tool boxes or machinery, the nature of the finish makes it ideal if the object is possibly a bit rough in its manufacture Box trailer makes love it. ( it makes things like spot welds disappear or at least look a lot better.) Being enamel it sticks very well, there is no need to sand it back just apply it.

One point mentioned is unnecessary its that of using a light coat first, there is no advantage in doing this.( spray painting myth) Put on wet it will be at its best to stick, if its put on light it may land as a lot dryer material having been dried by the air from the gun. this will make it less able to adhere properly.

You can also vary the pattern of the surface, put it on in a heavy coat and you will get large fish eye craters/hammer marks put it on thinner and the pattern will be finer. In other word keep the method you spray the same so that you get a more consistant all over finisn especially if you are doing large surface areas.

Put on at least two coats no need to go more than 3 you only need to wait about 10 -20 minutes between coats. Most brands are made to dry fast as that is one of their advantages in industry. No one would be intending to go back later to redo the object it would be paint it and get it out to be sold.

As the silicone is a problem don't spray it if you are close to things which you intend to paint with other non silicon products. Take it outside, paint somewhere where the overspray can't drift onto those things or cover everything up. Anything you paint should always be wiped over with a product like that mentioned Prepsol / wax and grease remover anyway but especially if you have hammerfinish around. Lastly spray out the gun with lots of solvent. ( do it a couple of times at least), and wash the gun. . Destroy any rags after use don't reuse them for anything else.

[Dengue]

I found the data sheet for the super etch Wattyl Spray Mate product I used here (http://www.wattyl.com.au/library/TDS/M1.02%20Super%20Etch.PDF). Being an etching product, my question is what would be the effect, if any, of using this over
a) the blue primer on the steel as delivered
b) existing ColdGal by another supplier

regards,
Jill

[Gavin Newman]

One point mentioned is unnecessary its that of using a light coat first, there is no advantage in doing this.( spray painting myth)

Not wishing to start an argument but the instructions for the hammer-tone I use (Solver) specifically mentions running a light mist coat then a wet coat, I've found that this provides less slump or sag when coating vertical surfaces than just running a wet coat straight up.

Others may have different experiences but it works for me.

Rgds - Gavin

[durwood]

Jill, no problem using it over the blue primer or cold gal but really a waste of material and time. If you use it it will add to the protection of the object though.

Gavin, if you put on a light coat obviously there is less material for the second to join to it and then sag. but as the second coat put on wet shouldn't sag anyway ( unless you overdo it) putting one coat on properly gives you a flat surface for the second one improving the end result just let it set up till it no longer is wet but tacky

A mist coat makes a smooth surface rougher and the end result is a worse finish. If you use the correct spray gun adjusted properly you won't get sags or runs. The mist coat system would help anyone who is a poor sprayer or has the wrong set up on the gun they are using.

The paint is meant to have two coats for proper performance, if you only use a mist and one you run the risk of missing areas or putting on too little in places. You need to put on a second for the correct amount which you will be spraying on a smooth tacky coat.

[Gavin Newman]

Each to their own, I've sprayed that way for many years and it works for me.