The Bunnings Workshop community can help with your home improvement projects.
I suggest trying Scotch-Brite 155 x 100mm Heavy Duty Scourer Pad with dishwashing soap and water.
If the blemishes still refuse to come off, I recommend trying Gumption Paste 750g Multipurpose Cleaner along with Rocket 100g Grade 3 Coarse Steel Wool.
Remember to scrub the frame in an up and down motion. It will take some time so please be patient and keep scrubbing until the blemishes start to come off. - EricL
I’ve got the most stubborn marks out of surfaces with Gumption, it’s fantastic stuff! - prettyliving
Workshop is a friendly place to learn, get ideas and find inspiration for your home improvement projects