Here’s a great weld-thru primer. It’s called 70-49 Metaflux Copper Spray and it is a high-density metal-coating that gives superb conductivity.

It also protects the inside of box-section or a seam that you are going to weld and makes striking the arc a cinch while it is said to almost eliminate splatter.

It resists temperatures up to 800-degrees C and bonds with any clean metal, steel, wood, ceramic, resin yada yada yada, pretty much any material you can think of leaving a high gloss finish.

A 400ml spray can costs £8.95 and is available from ENDS.