Can I rescue rusty metal?
Sam Glover TECHNICAL EDITOR Sam has broken down in a gigantic variety of classics over the years, then worked out how to fix them. John Simpson MASTER MECHANIC
Big John has worked at the greasy end of the motor industry since leaving school. Theodore J Gillam TECHNICAL EXPERT
Theo teaches automotive engineering and makes amazing things in his shed. Ed Hughes WORKSHOP GENIUS Ed singlehandedly keeps a fleet of obscure classics on the road. He’s never owned a modern car. Kim Henson CLASSIC CAR GURU
Kim’s been restoring classics for over four decades. BMC vehicles are his speciality. Nigel Clark DIY RESTORER Nigel’s driveway achievements rival those of professional mechanics. He’s our resident Triumph expert.
QMy workhorse Morris Minor lives outside. I’m bothered by a patch of corrosion near the rear window. I’d like to repair it, but I don’t have any specialist equipment. Where do I start?
AOur Minor expert, Matt Tomkins, advises that this is a notorious rust spot. It’s the meeting point of three panels and it’s regularly fed by leaks from the rear window seal. Your photograph shows a small pinhole surrounded by surface corrosion that’s been handpainted over in an attempt to keep it under control.
Given your lack of equipment, we’d recommend a minimalist approach to preserving the area. If the corrosion is as superficial as it appears, you’ll risk causing a lot more damage with a MIG welder due to the heat burning the paint, distorting the metal and blowing further holes.
Temporarily plug the hole with anything that will stop water getting in. This should always be your first action upon finding a rust hole.
Next, either seal the rear window or remove it and fit a new rubber seal with non-setting screen sealant. Most longterm hidden rust damage is caused by water finding its way inside the cabin, pillars, box-sections and seams.
Remove as much paint as possible from the corroded area using coarse abrasive paper. Scrape the seam carefully with a screwdriver or a thin spatula. Apply rust remover (not rust converter) such as Bilt Hamber Deox-gel. Agitate it with coarse steel wool or a wire brush. Wash off and repeat until the surface is uniformly shiny. Remove the interior trim and treat the rear of the seam in exactly the same way.
If no further holes have appeared, fill the pin-hole with a dab of an epoxy compound such as a hard body filler, Araldite, chemical metal, etc.
Spread the compound out a little on the back of the panel. Allow it to dry, then flat back the front surface. Put a thin bead of seam sealer onto the seam front and back. Make it as neat as you can on the outside. Apply a skim of body filler to the front and flat it back, repeating as necessary. Apply zinc primer to all bare metal surfaces, followed by filler primer. Flat this back with 600-grit wet-and-dry paper, then apply the topcoat.
If removing the paint and rust exposes a large hole or a series of small ones, then a proper Mig-welded repair is called for. Hand-file the hole to a neat
square or rectangle. Cut a slightly oversize piece of steel of similar thickness to the body (about 0.8mm). It should be easy enough to shape this to fit the hole using a vice, a hammer and a bit of gentle persuasion. When it slots in neatly, secure it with a tack weld at each corner.
Now go round applying more individual welds Work from opposite side to opposite side until the seam is continuous. Use a low setting on the welder, with just enough wire speed to produce a ‘frying-bacon’ sound. Grind the repair area flat using a rubber-backed abrasive paper disc in an angle grinder, then fill, prime and paint as previously detailed.