Advice on best approach - zinc/etch/under seal/ paint HELP

[D12typ]

Evening all, I’ve been reading various threads and I am of a mechanical/electrical bias in vehicles. A personal project of mine is a bmw 1602 restoration with a touch of resto mod. Either way…

I am in the process of stripping the underside and addressing rust (so far mainly in one location and a replacement panel has been sought)

So I am left with an underside which is a mix of built up original underseal, given it’s a 49 year old vehicle I’m very impressed as when taken back to metal it’s like new!

To the bare metal areas what should I apply? I have read several threads and some are contradictory to others.

Zinc vs etch vs epoxy

Then my approach thereafter is to apply dinitrol 447 and a cavity wax as final stage.

Appreciate your advice, i know this has been covered but want to understand the best approach for my car.

 

[Wildefalcon]

Zinc phosphate epoxy, then epoxy mastic, then something approaching your desired top coat?

 

[steveo3002]

epoxy is better than etch...no reason to not use it

 

[vw1]

Epoxy is your friend. My vw restoration will be called epoxy once finished.

 

[D12typ]

Thanks for the responses, what’s an estimated quantity of required epoxy primer for the underside and arches of an average car, appreciate it’s just an estimate

 

[steveo3002]

Thanks for the responses, what’s an estimated quantity of required epoxy primer for the underside and arches of an average car, appreciate it’s just an estimate

look at jotun...comes in almost 5ltr cans , would be enough

 

[Dcal]

You can get a zinc loaded epoxy (Jotun Barrier range for example) however there is so much zinc in it there is less room for the binder (glue) so it needs to be applied over a properly blasted surface (sa2.5) or it will not stick well.
This is true of any flavour of zinc rich coating and more so of the single pack versions. (Galvafroid, Zinga etc)

As has been said, a better option is epoxy mastic with added aluminium, against bare steel (I use Jotamastic 90A) then a second coat of 90A or a straight epoxy like Jotamastic 90.
They are designed to be applied over less than perfect prep (St2 as a minimum or better st3, but of course sa2.5 is better still)

There are lots of threads on here on the merits of one system over the other, but epoxys works for me.

Link below giving detail on how I preped the underside of my Alfa.
I've moved on to Jotamastic 90 from the 87 as its nicer to use.
As a rough guide it will take about 0.2 of a litre per coat of epoxy mastic per wheel arch and I'd suggest you give 2 coats.

25 year old Alfa 75 back from the brink (hopefully)

I use Dinitrol rc900 on bare steel for the same reason....basically as a rust converter and primer...then epoxy over the top. So far I've had good results.

www.mig-welding.co.uk