Monday, January 19, 2015

When rust spots blossom on rust free collector cars

What do you do when your collector car sprouts rust spots in the middle of the hood – an area that had no previous sign of damage?  If you’re a restorer with an inquisitive mind, you find out why it happened.  That’s what we did when this show-winning 1963 Continental Convertible sprouted a rust bubble in the middle of the hood.

The '63 Lincoln on the show field at Newport, RI
The rust bubble that got the ball rolling
We might not have dug deeply into this, if not for the fact that it had happened before, on the same vehicle.  Two years before we’d painted a rust spot on the hood and chalked it up to paint chipping or “causes unknown.” When a similar spot appeared in a different area we realized something had to be going on.

The something is rust from behind.  And when you look at the “behind” photo of this hood that is hard to believe.  There is no sign of rust on this hood; no sign that it ever had any problems.  But when we matched up the location of the rust spot on the front we found it matched the location of a spot weld where the inner frame was welded to the hood’s outer skin. 

The inner frame of the hood shows the voids where water was trapped
Once we saw that we realized there were probably more trouble spots around the other spot welds.  We removed the hood and stripped the paint to find 20 other incipient rust spots.

The hood, removed and stripped of paint

Little rusts spots were everywhere, hidden under paint



Here’s what happened:  Back in 1963, the folks in the Lincoln assembly plant welded the two pieces of the hood together without any surface treatment.  They used ordinary rust-prone sheet steel.  Once welded together, the hood was painted and sent out into the world.

The process of welding the egg-carton frame structure to the smooth outer hood panel created a number of areas where water could become trapped.  Over the next 50 years that is exactly what happened – every time water hit the underside of the hood a few drops worked their way through the gaps between the outer panel and the frame and they sat in the inner space, where rust began to grow.

It took quite a while, but by ten years ago, rust was starting to eat through the outer panel around the spot welds.  Left unrepaired, the rust would have eventually separated the two panels – sort of a “tear on dotted line” of rusted out spot welds.

All American cars of the 1960s and most foreign cars were made with this same technique. Some cars are still made this way today.  Luckily, most high-end cars today are made with steel that has been treated for corrosion resistance, and seams like these are often sealed after they are welded. Those techniques stop rust like this before it starts but they are no help on this 1963 car.

 
Studs welded over rust spots

A stud welder in use on a fender (not this Lincoln)

The big question for us was what to do about it.  Our body man came up with an innovative solution to put metal back into those rusted areas.  He used a stud welder to weld studs to the hood panel in all the affected areas.  The stud welder did not warp the sheetmetal of the hood as much as conventional welding, but it still put metal over the damage.  When we were done the hood was bristling with studs, which we ground off flush. 

We drilled into the frame behind the hood and sprayed Waxoyl rust treatment into the cavity.  We hope that will slow the process of corrosion from inside.  Short of cutting the hood apart and remaking it that is the best anyone can do. 

The studs have been ground off and smoothed

The hood, painted and ready to go back on the car
A small amount of glaze was used to level the hood surface as the welder made am impression a few thousandths deep.  Then the repaired panel was primed and refinished (front and back).

We fitted the sound deadening into place and finished the edges.  With a car of this quality we need to have the same finish on the inside that you see on the outside.  They didn’t care too much about that in the Lincoln plant but collectors today look for finish details like those. 

The fender tops are painted sans hood so paint flows into the undressed area smoothly
The assembled car, curing and ready for final buff and polish

With that in mind, we sprayed the tops of the fenders as you see to get an even finish across the top of the car.  Our cars are painted in modern Glasurit finishes and this blending technique is normal with that process.

The repair process you've seen here was used on a Lincoln.  The job would be essentially the same on a Chevrolet or even a Fiat.  We show a repair of a hood but this same assembly technique was used on quarter panels and other parts of car bodies, and these repair techniques apply there too. Rust-throughs at spot weld seams are more common than many people realize.

Experience with work like this is what distinguishes a restoration shop from a modern collision shop. Shops that fix wrecks are accustomed to doing fixed-price work for insurance companies. Rust is much less of a factor, and replacement parts are generally available. The goal of that sort of work is a quick repair that's "good enough" when seen from outside.  Discerning enthusiasts want more, and that's where specialists come in.  Look for lots more attention to detail, and more focus on repair than replacement because new parts are often not a viable option on 50-year-old cars.

In a repair shop, the final paint process may be the same on a 1955 car and a 2015 car, but all the steps leading from the car's arrival in our shop to it's rolling out the door will be different. And the paint process itself may be different as some antique cars are painted in "vintage" paint processes like nitrocellulose lacquer.  It's surprising how different the skill requirements for restoration and collision repair are. The process of finding and fixing all the incipient rust spots, and then finishing everything we touch to a high standard is time consuming.  But if you've got a rare and beautiful car that is what you want.


The finished result is shown below – better than new, and ready for parades and shows in 2015!

Best wishes
John Elder Robison

John Elder Robison is the general manager of J E Robison Service Company, independent restoration and repair specialists in Springfield, Massachusetts.  John is a longtime technical consultant to the RROC and other car clubs, and he’s owned and restored many fine vehicles.  Find him online at www.robisonservice.com or in the real world at 413-785-1665

2 comments:

William Walker said...

It would be so nice to have the manuals updated even for the old cars. The old manuals are sometimes hard to understand and it would be better to see one online. I just hope that all manuals will be accessible online from now on. http://www.cjsparesandrepairs.com.au

Jean Sunell said...

You're so smart! WOOF !