Quality primers?

[Burnerman]

Just before entering the asylum for good, I'm busy restoring an ancient chuff chuff council dumper
Try as I might I can't find a decent quick(ish) drying primer that is tough enough to last until I can get the top coat enamel on. Most, like Hammerite primer can be scraped off with a finger nail.
Any comments on the benefits between ordinary primer and acid - etch stuff, that I'm about to try?
John

 

[footprints]

Lots of primers need to cure before reaching full adhesion, for example Zinsser Bulls eye 123 is a great primer for lots of difficult surfaces like plastic but although dry in an hour it takes several weeks to fully cure in that time you can scrape it off with your nail.

 

[Burnerman]

I'm actually using Zinsser BIN for this wreck - although it's really for touching up external stuff its harder than Hammerite primer which doesn't kill rust either......no surprise there.
I'm just unsure what's involved here - obviously a primer sticks to the raw material and the paint then sticks to the primer. An etching primer should therefore stick even better to the parent metal - albeit at a price!
John

 

[JohnD]

It's steel you're painting?

how old is the vehicle?

are you spraying?

What will the topcoat be?

What is the most important characteristic you want in your paint system?

 

[Burnerman]

Its a 1982 single cylinder ex council dumper fabricated from steel channel and plate, some of which is 2mm or 3.5mm thick.
Its rusty, mostly solid but I'm making a new curved base for the skip. I'm only able to roll 2mm which is thinner than it should be but I'll reinforce that later. I'll remove as much rust as I can and the finish will be Benford yellow enamel, brushed on.
John

 

[JohnD]

It might originally have been finished in tractor paint (not cellulose or synthetic) which may still be available.

Under coach paint I've used Red Oxide primer which is good for temporary protection between stripping and finishing (you can't use it under cellulose or modern car paint)

 

[Burnerman]

I've already bought and used the brushing enamel which gives a very acceptable finish on the bits that I've done.
I have to work outside so a fast drying primer is ideal.
I'm trying to ascertain whether etching primer is better than the standard stuff.
John

 

[JohnD]

Is the brushing enamel a White Spirit paint?

 

[Burnerman]

Pretty sure it is, but I haven't needed to thin it yet.....there aren't any instructions or recommendations on the can.
John

 

[JohnD]

that's a pity

you can use red oxide if it is (but test a sample first)

for rust protection, two thin coats are better. Less brushmarks, and the second coat should fill any pinholes or thin spots. I'd use Kurust on any rusted patches after you have wirebrushed them. You can paint over the modern version.

Ask the paintmaker. They will either offer, or recommend, a system of compatible materials.

 

[Burnerman]

I'm sure the oxide primer would be fine, whatever the top coat is, it's not cellulose.
There is no info on the can at all or makers name.
I've used red oxide before but it took an age to dry and looking at areas which have been scratched off, adhesion wasn't that great.
Hence the thought about etching primer.
John

 

[JohnD]

it contains lots of solids, is supplied thick, and thick coats harden poorly. Perhaps intended for sloshing onto bridges and structural steelwork. I find better results thinned a bit, and each coat left a week. While the solvent is still present, it repels water.

On steel, I think protection from rust is the most important feature.

I haven't used an etching primer.

 

[Burnerman]

I'm sure its a replacement for the old red lead, of which I've used gallons
Anyway, I intend to use the etch primer on the welds as I go so I'll see what happens.
John

 

[Avocet]

I might be a bit late to the party here, but in my limited experience, zinc-rich primers are great, PROVIDED there is no visible rust on the surface being primes when they are applied. I've never had much luck applying them to steel where any rust is present at all. Not just the removal of visible, crispy, flaky rust, but even stuff you'd need a magnifying glass to see.

This site has (what I think is!) a lot of good advice:

https://www.rust.co.uk/

My current favorite potion (although I haven't been using it for long, so I can't give any kind of useful testimony yet) is this epoxy mastic which can be painted on to (stable) rust:

https://www.rust.co.uk/product/cat/em-121-epoxy-rust-proofing-chassis-paint-7

I've done a few repairs on my old Alfa a couple of years ago, and so far, it is still sound. You're not supposed to paint over it (at least, the sort of high quality finish that a car body would have) but I did so. It's very hard to rub down. I also got a few bubbles as a result of solvent entrapment. However, it does seem to have been effective in adhering to the steel underneath! It certainly outlives Hammerite, Rustoleum and POR 15. The only thing I would say, is that you really need to degrease and de-salt the surface thoroughly first. Hot water and strong detergent is best, rather than a solvent like acetone, thinners or brake cleaner, because they dissolve the grease but unless you're using gallons of the stuff, they just dilute it and redistribute it over a larger area but in a thinner coat, once they evaporate.

 

[EddieM]

Just before entering the asylum for good, I'm busy restoring an ancient chuff chuff council dumper
Try as I might I can't find a decent quick(ish) drying primer that is tough enough to last until I can get the top coat enamel on. Most, like Hammerite primer can be scraped off with a finger nail.
Any comments on the benefits between ordinary primer and acid - etch stuff, that I'm about to try?
John

And there was me thinking my hobbies were odd.