Battery compartment surface rust; how would you treat this area?

[WoGGo]

Some time ago water was getting into this area via the perished tail light seals.

I need to change my battery so I'm looking to address this issue whilst the battery is out.

I'm not looking for perfection, but given I have no experience in this area, what would be easiest/simplest way to fix this and prevent further rust from spreading?

I have a brand new battery tray and nuts if that is relevant.

[Rokoz]

Wire wheel/grinder to remove all of the rust and paint. After it’s completely clean use epoxy primer and paint of your choice SEM 62233 is a pretty good match for the green.

You will want to remove those metal plugs and get some plastic ones

[Big Nodge]

I’m dealing with this on my e36 and am planning to use POR-15, it’s a little more forgiving on the rust removal aspect.

[Cubieman]

I ground it down really well and used POR-15, did this on the bracket as well.

2K epoxy aerosol primer if you want a quick and durable primer coat before the paint.

[WoGGo]

Wire wheel/grinder to remove all of the rust and paint. After it’s completely clean use epoxy primer and paint of your choice SEM 62233 is a pretty good match for the green.

You will want to remove those metal plugs and get some plastic ones

SEM 62233 is not available in Australia; would Rust-Oleum Stops Rust Custom Spray 5 In 1 Spray Paint (Satin Earthy Green) be a decent substitute?

https://www.bunnings.com.au/rust-oleum-340g-satin-earthy-green-stops-rust-custom-spray-5-in-1-spray-paint_p0489940

Which metal plug are you referring to; do you have a part number?

[WoGGo]

I ground it down really well and used POR-15, did this on the bracket as well.

2K epoxy aerosol primer if you want a quick and durable primer coat before the paint.

Which product are you referring to exactly; POR-15 Rust Preventive Coating or POR-15 Top Coat DTM Paint?

[Cubieman]

Which product are you referring to exactly; POR-15 Rust Preventive Coating or POR-15 Top Coat DTM Paint?

I just used the POR-15 topcoat I think "detail" paint, gray cast aluminum color for my silvergray car, then POR black (non rust) on the bracket for the battery.

I used some of that "rust dissolver" you put on rust and wash it away, again, my rust was minimal.

If I was to do it again I would use an epoxy based primer and then topcoat.

This specific case seems to have a fair amount of rust so maybe POR rust prevention paint, then someone over that for the color.

I would start grinding down to bare metal to see how bad it is, if there was for instance holes in the metal from rust you want to use a rust preventative paint. If it's just surface rust clean it up, all of it, and use some quality paint.

You can always do the rust preventative POR and then fine tune it with a topcoat of your choice that matches the best.

Definitely going to need to get various dremel attachments to get all the rust out of there, thats the main thing.

[BMWE46M3]

I've been restoring my 1997 M3 and highly recommened Bilt Hamber Hydrate-80 https://bilthamber.com/product/hydrate-80/. I've used POR before but find Bilt Hamber to be a much better product. After cleaning the surface I used wire brushes/wheels to remove the loose rust. Then apply Hydrate-80, then SEM 62233 (light green). BH also has a zinc-based primer which I've used as well between the Hydrate-80 and SEM steps. Another excellent product. https://bilthamber.com/product/electrox/ I buy these products from Carzilla https://carzilla.ca/ and they ship to North Carolina. They have had some limitations shipping to the US lately due to tariff issues but if you reach out to them they will will ship to you. Attached are before and after pics of my undercarriage for reference. Hope this info helps.