When I pick up scrap iron it’s usually filthy with paint, grease, and other unmentionable substances. So it needs to be cleaned. Heating it up to red heat is an excellent cleaning method, it removes old paint and grease and any plating, and as a bonus softens hardened steel. Not bad for a single process.
I have been throwing the scrap in the bonfire to clean it, but that was very hit and miss, sometimes it just didn’t get hot enough. So I made a furnace out of this odd shaped drum, about 40l capacity I’d say, and an old computer fan. I cut a hole in the side wall of the drum at the bottom and inserted a piece of steel pipe that I had lying around, it’s about 600mm long. The fan is duct taped to the end of the pipe, making sure that it is blowing into the drum. I used a 240V fan but a 12V fan would be much safer. It is necessary to cool the tube with the fan to stop the fan getting too hot, I used an old shirt about halfway along that I kept wet.
To use simply get a good armful of firewood, I use softwood pallets since I can pick them up for free. It works best of the wood is in short lengths, maybe 200mm max. Start the fire with a newspaper, then the firewood, then turn on the fan when it is alight. Wait until the wood has burned down a bit, then load the drum up with your scrap iron. In 10 minutes it will all be red hot and the iron will be nice and clean.
Don’t breathe in the smoke, it will contain whatever was on the iron. Stick to getting your trace metals from cornflakes.
When it has burned down, tip out the iron and clean with a wire brush. Then wait for it to go rusty, which will be overnight since the iron is so clean.
I couldn’t take a photo when it was red hot, the heat was just too intense.
The white coating is zinc oxide from the galvanised plating burning off. It comes off easily.