Raw vs red oxide primed steel: which should you order?

When you order steel from our Order Steel page, you'll be asked whether you want it raw or red oxide primed. It's a small choice, but it's worth getting right. Here's a plain guide to help you decide.

What is raw steel?

Raw steel is supplied as it comes from the mill. Hot rolled sections such as beams, columns and channels usually have a dark grey, slightly flaky surface called mill scale. Raw steel has no protective coating, so if it's left outside or in a damp place it will start to show surface rust fairly quickly.

What is red oxide primed steel?

Red oxide primed steel has been given a coat of red oxide primer before it leaves us. The primer gives the steel some protection against rust while it's stored, delivered and built in, and it gives a better base for paint.

It's important to know what primer is and isn't. It's a primer, not a finished, long-term protective system. On its own it won't protect steel exposed to the weather for years.

When raw steel makes sense

Raw is often the better choice if:

• The steel is going to be galvanised. Galvanising needs clean, bare steel, and primer would have to be removed first.
• It's going to be powder coated or painted to a specific system. Many coating systems start with blasting the steel back to bare metal anyway.
• You're going to do a lot of welding. Primer burns and gives off fumes when welded, and it can affect weld quality, so it usually needs grinding off around the joints.
• Your engineer or architect has specified a particular coating that needs to go onto bare steel.

When red oxide primed makes sense

Primed is often the better choice if:

• The steel is going into a house extension or knock-through and will be boxed in, plastered or protected as the engineer specifies.
• It will sit on site for a while before it's built in, and you want to limit surface rust.
• You plan to paint it and want a ready base to work from.
• You're doing only small amounts of welding or drilling and are happy to grind back and touch up those areas.

Things to check before you order

• Look at your engineer's spec. It may say how the steel should be protected, including fire protection. Some fire protection coatings need a compatible primer, so check before ordering.
• Ask your builder. They'll know how the steel will be handled, fixed and finished on site.
• Think about where it's going. Inside a dry, heated home is very different from an exposed external frame.
• Touch up any damage. Cuts, drill holes and scratches from handling can expose bare steel, so keep a tin of primer handy.

Still not sure?

If you're stuck between the two, give us a call on 01603 560808 or WhatsApp us on 07824 656634 with details of the job. We'll talk it through and help you pick the right option. Stock sizes are usually ready in 2 to 3 working days, with free collection from Rackheath or delivery within 15 miles.