Primer Before VHT Paint?

[Onoff]

I need to paint this "louvre" panel made from an old oil drum.

I'm a bit worried about residual oil on the metal so was thinking to stick it through the dishwasher on the quiet...

As for paint, I don't really want to go and buy any. I've some black VHT which says it doesn't need primer. Also some etch primer. Would the VHT go over the etch primer?

 

[Parm]

That’s nicely made

 

[Onoff]

That’s nicely made

Thanks but don't look too close!

 

[Kram]

Flap disc then VHT paint in my opinion, skip the primer. If its recently been in citric Id skip the flap disc too. Finish with gentle heating as it will dry but wont fully cure untill it bakes a bit.

 

[Onoff]

Flap disc then VHT paint in my opinion, skip the primer. If its recently been in citric Id skip the flap disc too. Finish with gentle heating as it will dry but wont fully cure untill it bakes a bit.

It's not been in citric but I was thinking of it. I'll need to flap disc it to get rid of some of the heavier rust anyway. What concentration citric do you think and should I wash it off or just air dry then paint?

 

[Kram]

I wouldnt rinse, I think its better protected with some residue, just wipe or air dry in a warm or hot place. Flap disc is probably quicker.

 

[Onoff]

I wouldnt rinse, I think its better protected with some residue, just wipe or air dry in a warm or hot place. Flap disc is probably quicker.

More looking for a half decent surface to paint so flap disc it is!

 

[Ross365]

I once asked Johnstone's about what temperature their zinc phosphate primer (which I use a lot) would cope with. They said it was OK with central heating (~70'C) but no higher. Not sure that an etch primer would do better.

 

[Blue Chips]

As for paint, I don't really want to go and buy any. I've some black VHT which says it doesn't need primer. Also some etch primer. Would the VHT go over the etch primer?

When I fabricated our backyard firepit/firebox, I used VHT paint with NO primer. That was about 8 or 9 years and many fires ago, and the paint is still in good shape...no flaking and virtually no rust. I tend to build the fires in the center of the box so that there is a bit of air space around them, but the metal still gets fairly hot.

I prepped the metal (hot-rolled 1/4-inch mild steel) by removing every last speck of mill scale by blasting the surface using a grit blasting attachment on my pressure washer. As I recall, the media was coal slag, which left a somewhat roughened/keyed surface that I believe gave the paint an excellent mechanical connection (bite) with the metal. A touch of flash rust formed immediately after the water-grit blasting, but it doesn't seem to have affected the longevity of the paint, since it's still going strong.

Old photo:

A few days ago (2022 winter solstice):

 

[MetalMonkey]

No primer and very thin coats.

 

[Wildefalcon]

And cook the coats in-between each layer.

 

[Alan Reynolds]

I use VHT on kart exhausts. As already said, no primer or old paint, no oil and lightly keyed, first couple of coats dusted on and warmed on, don’t burn it. Subsequent coats should be thin coats and works best.

 

[James1979]

I sell a lot of fire pits. They’re all UHT painted, not Simoniz but same principle.

Mine are all shot blasted then wiped a few times before paint. No primer.

It’s the curing that is important.

 

[Onoff]

And cook the coats in-between each layer.

Thanks, at what sort of temperature?

 

[Onoff]

I prepped the metal (hot-rolled 1/4-inch mild steel) by removing every last speck of mill scale by blasting the surface using a grit blasting attachment on my pressure washer

I was thinking of getting such an attachment for my Kärcher. What one did you get?

I've 50kg of blasting sand (proper stuff) sat here from my failed attempts with my underpowered compressor and when the sand kept clogging.

 

[James1979]

Thanks, at what sort of temperature?

get the data sheet and see what they say.

I use mipa and you dust lots of light coats on. Previous coat only needs to be touch dry.

Then cure it in one at 400 for an hour.

They expressly tell you not to cure between coats as it doesn’t work properly.

What @Wildefalcon uses is different again I’d think.

Simoniz tech dept is who you want it be asking.

 

[Porkypine]

I used Simoniz on a small steel part, it was absolute rubbish and came straight off...
The part was clean, dry and grease free so not my fault!
Interested to find a decent rattle can hi temp paint that stays on..

 

[bricol]

I followed the instructions on the side of the Simoniz can - blasted, cleaned, dry, no primer etc.

Impressively long lasting several years in.

 

[Porkypine]

I followed the instructions on the side of the Simoniz can - blasted, cleaned, dry, no primer etc.

Impressively long lasting several years in.

Must have been just me then, can't see how but..

 

[Onoff]

get the data sheet and see what they say.

I use mipa and you dust lots of light coats on. Previous coat only needs to be touch dry.

Then cure it in one at 400 for an hour.

They expressly tell you not to cure between coats as it doesn’t work properly.

What @Wildefalcon uses is different again I’d think.

Simoniz tech dept is who you want it be asking.

I'd should have read the can!

"Bake for 1.5 hours, gradually building up to 220degC"

Can't be any worse than when I was curing the positive photo resist spray that smelt like wee.