Soldering Hot rolled mild steel

I need to SS 4 pieces of hot rolled 6mm sheet together. Since the steel has an oxidisation coating on it I guess its not a good idea to solder straight to it. Removing it seems near impossible - any ideas?

fizzy,unless you want to take it off with emery cloth, or file it, you can use either the electrolytic rust removal system, or soak it for a day or so in citric acid, or similar. Although I find that brazing with Oxy A, or propane, with a neutral flame you don't need much of a clean up at all. Ian S C

I usually clean up the surface with an angle grinder. Colin

Angle grinder with wire brush- must wear goggles. Acid flux, Bakers , solder will stick to all the cleaned bits no problem.

Not Bakers, acid, fizzy want to silver solder, so an appropriate flux, or as I usually do borax. Ian S C

Sorry, I read SS as soft solder. For some reason I assumed he was soldering the sheets together prior to machining.

Gordon, you could be right, fizzy can take the one that suits. Brazing little bits of steel, I use scrap sheet brass cut into strips about 5 mm wide, and borax for flux, works ok for me. Ian S C

Try dilute Hydrochldoric acid (Brick cleaner) to clean steel sheet - wash off with clean water and coat joint area with Borax paste - clamp in position and heat to just under cherry red and apply Silver Solder to edges of joints - solder will flow towards flame/heat position (Capillary action) - let cool normally - DO NOT COOL IN WATER - causes brittal joint