uv damage?

[NutmegCT]

Good morning folks. My 76 MGB was repainted at least 5 years ago, black over the original red. The horizontal surfaces (boot cover and bonnet) show blotchy or streaky areas; I take this to be uv damage, as the areas shielded by tonneau or hood cover show no such problems. The sides are excellent, deep rich black; the paint is excellent condition, no flaking, crazing or peeling; orange peel surface.

What can I do to restore the finish of the bonnet and boot? I've tried hand rubbing with Meguiar Scratch-X and 3M scratch remover, then NXT wax. No difference.

Thanks.
Tom

 

[PC]

Do you know if the paint is a two-stage (clear over black base) or single stage (black only)? It can make a big difference.

It sounds like you are probably correct about it being UV damage. It's very common that horizontal surfaces take a heavier beating by the sun and oxidize much faster than other surfaces. They are also more susceptible to damage by fallout contamination. The big question is "how deep does the damage go?" If it's only the top few percent of the coating you can probably bring it back just fine. If its 50% or more there's a much greater risk when buffing it out.

You basically need to remove the damaged paint and reveal what good paint is left. Using Scratch-X and 3M scratch remover was a good first try. They do a good job on very light oxidation and will also "round off" very small scratches but are only effective if the damage is limited to a very small percentage of the coating depth. The wax will only seal and protect the top surface. You need to fix the problem first otherwise you're just protecting a bad surface.

Deeper damage means you have to cut off more material using more aggressive products (cutting compounds). Megiar's makes a number of products for this purpose (3m and all the others make similar products). The three that come immediately to mind are #2 fine-cut cleaner, #1 medium-cut cleaner and #4 heavy-cut cleaner. These must be applied with a high-speed rotary buffer. Using a rotary buffer requires skill and practice so all but the most intrepid DIY'ers are better off deferring the job to a professional.

If you do have a two-stage finish you must be even more careful. Clear coats do a nice job preventing fading but they are much thinner than single stage finishes and are softer too. You can grind all the way through a clear coat very quickly.

Whether it's two-stage or single if the damage is deep or you grind all the way through while trying to fix it you're looking at a re-spray. Talk to your painter.


PC.