Welding repairs to corroded panels.

 
The front panel on this Mk1 ford transit was weak and holed. The cross member behind it was also rotten and full of lose scale and debris which could be heard rattling about inside the box section.Removing the top of the front valance revealed the cross member behind it had corroded through at the front edge where it met the front panel.This is a structural part of the vehicle so had to be repaired by letting in new metal.
 
First job was to tidy up the holes cutting out the rust and getting back to sound metal with an angle grinder.The front panel had been repaired in the past by simply plating over the holes,effectively sealing in the rust.These old repairs were removed and the edges of the front panel were then cut back to sound metal and squared off.
A strip of metal long enough to cover the resultant hole was cut,at the front a 1/2 inch flange was bent over to meet with the bottom of the front panel.As this section of the front panel is curved 'V' sections were cut out and the replacement section curved to fit,when the fit was OK the cut sections were seam welded together and the new section tacked into position.A few adjustments and then the new section was seam welded to the cross member and front panel.
A new section of front panel was then welded into place.The curved section was formed by hammering a strip of sheet steel over a wooden block to shape it.Sheet metal that has been shaped in this way is more resistant to bending than flat section and contributes to the rigidity of the structure.It's important to protect all repaired areas from corrosion as soon as possible.

Removing rusted fittings and fixings.

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Repairing rust holes with fibreglass.
 
Easier than welding but not suitable for structural areas.
A small rust bubble on a front wing turned into a larger hole when attacked with an angle grinder.This damage is not in a structural area.The rest of the wing was sound and to minimise paint damage fibreglass was used on the repair.The hole was enlarged,cutting back to sound metal and the whole area treated with a rust remover/convertor.The area was then carefully dented so that a layer of glass and resin could be applied without it standing proud of the original contours.
Fibre glass resin and mat was applied to the cleaned rear of the panel and when set other layers were applied to build up thickness.The repaired area was strong and will not rust although eventually some corrosion will probably make its way through elsewhere.
A skim of filler and the wing is ready for paint.Most car filler is porous and absorbs water so it should be protected by primer and top coat as soon as possible.Body filler should be applied to bare metal or fibre glass,it will not key well to existing paint.The area behind this repair was easily accessible and treated with a rust preventer then painted,this should keep it sound for a fair time
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 Welding repairs to bodywork.
 
A Mercedes 307D with a rotted out windscreen surround.
 This shows what rust and corrosion can lurk under rubber mouldings.Taking the cracked windscreen out of an old merc revealed this hole.Most of the metal the screen rubber fits into was missing.Rot round a screen surround is bad news and often difficult to repair. Before removing the screen and again before starting to remove the corroded metal lots of card patterns were made to provide a record of the shape.As the windscreen and rubber fit into the recess it needs to be accurately shaped to avoid causing still more leaks.I found similar corrosion when taking the screen out of my old London taxi,water leaking behind screen rubbers usually finds its way into the interior of the vehicle causing corrosion to spread in other areas.
As the shape was quite complex with various curves small pieces of steel were welded to the back panel leaving what was left of the front in place to give a guide to the shape and length.This was easier than trying to form the missing section from a single piece of steel.When finished the small sections were welded together
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Covered with a skim of filler the panel looked better and at least should hold the windscreen in place.Repairs should be primed,then covered with a gloss paint for complete protection as quickly as possible and this should be done on a dry day.Primer or filler are both porous.Damp steel corrodes very quickly and metal that has been welded corrodes at an alarming rate if it is not covered and protected..

 

Simply plating over a hole with the new metal overlapping the edges leaves an area of unprotected metal which will carry on rusting behind the new patch.It will soon spread to the back of the patch and lead to an even bigger hole.Cutting out the rusted metal completely and then butt welding in a new section with the welds ground down and both sides painted and protected gives a longer lasting and neater repair.Don't forget to disconnect the battery,alternator and any sensitive electronic componenets (alarms etc) when using an arc or mig welder on any vehicle.Welded repairs will rust quickly if not painted,the heat from the welding torch burns off any residual protection from oil,grease or paint and corrosion sets in fast.Likewise steam cleaning a chassis or engine leaves bare metal unprotected and damp,ideal conditions for corrosion.
Many rust removers or convertors contain phosphoric acid to neutralise existing rust and some primers contain zinc to discourage further rusting.There are many oils and liquids which it's claimed slow or stop rust from spreading.Some of the common treatments include Waxoyl.Dinitrol,Kurust,3in1 and Eureka Fluid Film.Rust bubbles on paintwork usually indicate rusting under the paint coming through from the back of the panel,and usually the rot is much worse on the back of the panel.

Before welding,check for carpets,wires etc on the reverse side of the area to be welded,disconnect the battery and alternator and have at least a full bucket of water on stanby in case of fire.

Links to mig welding forums,welding hints and tips..

Welding Forum
A forum full of welding information.Lots of info on mig welders and welding techniques.
Motor City Welding Tips
More welding tips,welder tests and other info.Well worth a look.
Mig and arc welding videos.
Videos covering various aspects of mig or stick welding.Faults,buying equipment and techniques.
Restoring a Rover P5B.
Some people say these are the best cars Rover ever made.

Transit motorhome page.
AF (Imperial) tools for sale.
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