Why burglar bars rust within a year, and how to buy ones that do not

Security steelwork that fails early nearly always fails the same way: rust bleeding out from under the paint within the first rainy season. The welding is rarely the problem. Preparation is.

Mill scale is the culprit

New steel arrives with a thin blue-grey layer from the rolling mill. It looks like a finish. It is not — it is loose, and paint applied straight over it is bonded to a layer that will come away. Water gets underneath, and the rust travels sideways beneath a coating that still looks intact.

What proper preparation looks like

Steel should be degreased, then sandblasted or thoroughly mechanically cleaned back to bright metal, then primed and coated while it is still clean. Leave blasted steel out overnight in Harare humidity and you have to do it again.

Questions worth asking before you order

• Is the steel blasted or just wire-brushed?
• Is it powder coated and oven cured, or brush painted?
• Are the welds ground back before coating, or coated over as they are?
• What happens where the bars meet the wall — is the fixing point coated too?

That last one catches people out. Bars are often cut to length after coating, leaving raw ends buried in the wall where nobody can see them rust.

What good costs

Proper preparation adds perhaps fifteen percent to the price of a set of burglar bars. It roughly triples how long they look acceptable. If a quote is dramatically cheaper than the others, this is usually the step that was removed.