How to rejuvenate mid century steel window frames?

SaBB

Firstly Hello and thank you to this amazing community! I cannot overstate how much this blog has already helped me fixing and improving things in my home, being a novice in terms of home ownership and DIYer!

I'm trying to get my steel window frames back into shape – I love the sleek, slim profile but they really are high maintenance to keep rust at bay with the typical condensation that comes with them ... I have a few issues that I would love some advice on.

1. 'Rust blisters' creating holes in steel frame
I started with sanding the rusty bits on the frame and found one bit that appears to be hollowed out ... I have sanded it as much as possible and treated with rust converter – however, I'm unsure how much more should I take off – without compromising the frame. I also assume I should fill the holes with something? See photo 1

2. After realising how many layers of paint are on these frames, I decided to strip them completely (rather than just sanding the paint surface). I started manually but got advice from my neighbour to use something like Orange Peel Stripper. Now I'm wondering if this will impact all the silicone adjacent to the glass and if I'd have to re-seal them? I have also heard that 'sealing' these frames traps moisture in them – so I'ma bit confused on what's the best thing to do here?

My understanding is that I need to sand over the applied rust converter to make the new enamel paint stick. Do I need a primer or will the rust converter treatment and sanding suffice?

3. Last but not least – how often do you repaint steel frames? Do I need to do this every year or should this last a couple of years if done properly? I'm wondering, because I have considered replacing the windows entirely (I have to preserve the heritage look, which would make it an expensive custom job). 

In case you're wondering, yes, I will need to replace the window sills, they rotted from underneath and the sides – but this is a problem for another day. 

It's probably not a big job but I am a little overwhelmed at times. I don't mind putting the work in but I'd hate to do it wrong and cause more harm than good. Thank you everyone in advance!! I appreciate any feedback.  

MitchellMc

Welcome to the Bunnings Workshop community @SaBB. It's sensational to have you join us, and many thanks for your question about repairing a window frame.

First off, you're doing a fantastic job already, and you really can't cause more harm than good with this type of repair, so don't let the process overwhelm you. It’s totally normal to feel that way, especially when tackling something new and intricate like steel frame restoration. You're clearly approaching this with care and thought, and you're well on the right track.

In terms of longevity, a proper restoration like the one you're working on can last many years—possibly up to a decade—before requiring attention again, though that does depend on environmental conditions and maintenance. That said, your frames are showing a fair bit of wear, so this first major round of work should make a noticeable difference and set you up for longer intervals between touch-ups.

Any rust that flakes off or can be chipped away isn’t offering any structural support, so don’t hesitate to fully remove it with a wire brush, scraper, or sander. You’re doing the right thing treating it with a rust converter. Once dry, fill any holes or deep pitting using a two-part epoxy putty—this gives you a strong, sandable fill. Make sure you don’t overfill, as sanding hardened putty down can be quite the task.

Paint strippers can be very effective, but they may soften adjacent silicone seals. If this happens, you’ll likely need to re-seal those edges once you’ve finished painting. Using silicone after the paint job won’t trap moisture as long as the metal was properly prepped, treated and sealed beforehand—this is the key to avoiding corrosion under the surface.

You’ll definitely want to sand over the rust converter to smooth the surface and help the primer stick. A metal primer is strongly recommended—even if you've used rust converter—as it ensures adhesion and adds a further layer of protection. From there, a couple of coats of water-based enamel will give you a durable, easy-to-clean finish.

If done properly, this isn't something you'd need to repaint every year. If you’re seeing rust come back annually, that usually indicates moisture getting in somewhere, like the inside of the frame. With a good rust treatment, filler, primer and enamel coat, you should get multiple years out of your hard work.

When working around glass, especially when scraping or sanding steel frames, it’s really important to wear appropriate PPE—safety glasses, gloves, a dust mask, a long-sleeved shirt, trousers and enclosed footwear. Be careful not to knock the glass as it can shatter easily.

Please let me know if you have any questions.

Mitchell