c3 front end rivets showing

[Robert M.]

anyone know how to repair the area above the headlights, the rivets bulged the paint and fiberglass, have humps showing?

[Michael W.]

Re: c3 front end rivets showing

Given enough moisture, they all do that. A steel brace and aluminum rivets under minimal body work was not the best engineering move. Not much choice other than to to strip the area, remove the corroded rivets and start the process again.

[Alan S.]

Re: c3 front end rivets showing

Hi Robert,
I see by your membership number that you're a new member so HELLO and I'm glad to see you on the board.
Many owners consider the 'bumps' a badge of honor since it's seen on so many original paint cars.
The fellow who helped me with the paint prep for my 71 felt there was no rust on the header rivets and that a cosmetic repair would be a good solution. I'd think having someone with some fiberglass experience look at your situation may be a good idea.
The car has now been painted for 5 years and so far his advice has been very good.
Here's a picture of what work he guided me through. The car is painted with acrylic lacquer.
Regards,
Alan

https://www.forums.ncrs.org/attachment.php?attachmentid=26802&stc=1&d=1283030293&uid=4710

[Jack H.]

Re: c3 front end rivets showing

This is usually the result of galvanic action (dissimilar metals, aluminum rivet & steel header bar, separated by a dielectric, fiberglass, when fed an ionic solution, salt water, creates a 'battery'). Those who have done the 'surgery' required to remove the fiberglass covering these 'bumps' have generally discovered a 'strange' white powder.

That's aluminum oxide. The result of rivet surface corrosion + migration up the rivet to the head.

You can sand the body fiberglass flat and re-paint, but in most cases this is only a temporary fix as the rivets will continue to oxidize and the bumps will return in a period of time.

The archives have prior posts on this common to early Shark car malady. In most cases, the only PERMANENT fix is to drill out the rivets (eliminate the aluminum) and re-fill the holes with fiberglass.

Note I said fiberglass and NOT bond! Raw bond will continue to shrink over time and the 'bumps' will re-appear in reverse (circular depressions). Most don't want to hear this because it means more work than a simple fix...

[Dick W.]

Re: c3 front end rivets showing

The root of the problem is galvanic corrosion caused by two dissimilar materials, steel and aluminum. The proper way to repair this is to remove the rivets and the reinforcement bar, properly fill the holes, bond the bar back to the lower side of the upper surround with a bonding material similar as to what was used to bond the panels together. If total authenticy is what you are after, you can cut short pieces of rivets off and epoxy them in the holes in the reinforcement. That way it looks like they are still in the bar. GM did away with the rivets about 1974 and bonded the bar in for the rest of the C-3 production

[Joe L.]

Re: c3 front end rivets showing

The best illustrated tutorial I've seen on this repair was written by Ralph Eckler and appeared in an edition of Vette Magazine MANY years ago. I know I have that edition here but I don't know which one it was and I'd have to go through a lot of magazines to find it. If anyone knows the edition, I might be able to find it.

[Robert M.]

Re: c3 front end rivets showing

thanks guys, it all sounds like a big job, maybe let them alone is a good idea.

[John H.]

Re: c3 front end rivets showing

I own original paint/owner with rivet area that can be seen when up close.
If the car still has original paint, PLEASE consider leaving it alone. If the area
is not that bad, then leave it alone. That is my suggestion.

[Joe L.]

Re: c3 front end rivets showing

I own original paint/owner with rivet area that can be seen when up close.
If the car still has original paint, PLEASE consider leaving it alone. If the area
is not that bad, then leave it alone. That is my suggestion.

John------


The problem is that once the corrosion starts the "bumps" will continually get worse as more and more of the aluminum metal is converted to aluminum oxide. The aluminum oxide occupies more space than the aluminum metal and that's why the "bumps" appear.

[Pat M.]

Re: c3 front end rivets showing

John------


The problem is that once the corrosion starts the "bumps" will continually get worse as more and more of the aluminum metal is converted to aluminum oxide. The aluminum oxide occupies more space than the aluminum metal and that's why the "bumps" appear.

Joe, the bumps on my 70 have not gotten worse in the 5 years I've owned the car. But, I don't drive it in the rain, and I keep it in a climatized environment, so perhaps it's because there is no longer a moisture catalyst to fuel the galvanic process.

[Jack H.]

Re: c3 front end rivets showing

YES! You've removed the 'forcing function' (exposure to moisture) and converted the car from daily driver to 'weekend warrior' service. So, you logically expect to see what you do see--expansion of 'bumps' is slowed to a snail's pace and/or stopped.

But, I actually drive/use my '71 (+65K miles since frame off) and those pesky bumps grew to the point of looking so bad/obvious that I did the 'surgery' to eliminate them.

The only 'good' thing associated with seeing them on an older Shark is you pretty much know it wasn't front end damaged in its prior life to the point of requiring MAJOR front clip repair...