Experienced Painter Advice Needed
 

I was looking at the paint on my roof this morning and looking closely, noticed rust spots about the diameter of a pin.
I only see these spots on the roof and lower rear body panel in/on the Colonial white paint.
What happened to the paint and what would be a repair? Was the surface contaminated prior to refinishing? Will the paint need to be sanded, new paint and clear coat to seal?
Would a good waxing prevent further deterioration?
Will be moving the car to AZ soon and expect that lack of moister will slow the progress.
Advice appreciated!

Re: Experienced Painter Advice Needed
 

Wax will help, if it's stored inside in Arizona, I don't think I would worry.

Re: Experienced Painter Advice Needed
 

A lot has happened since the mid 50s. As the paint deteriorates, it gets more porous. If moisture can find a way under, corrosion can start. The only way to stop the cancer is to remove it or at least neutralize it. This would require a refinish so you will have to figure on repairing it before it becomes a problem. In AZ, it may take quite a while for it to become a problem that will require immediate action.

Re: Experienced Painter Advice Needed
 

Dealt with a lot of forensics paint defects; Is this the original finish or has it been refinished at some point in the past? Close up photos would be a great help.

Re: Experienced Painter Advice Needed
 

Paint forensics guy here. Is this the original finish or a refinish? Close up photos would be a great help.

Re: Experienced Painter Advice Needed
 

Will get some close up photos soon, have been off this page for a bit, thnx.

Re: Experienced Painter Advice Needed
 

Weather is not cooperating here in SoCal, Th looks good? for some photos.

Re: Experienced Painter Advice Needed
 

have you done any grinding or use a cutoff wheel those little sparks are molten metal and will do damage to paint and glass

Re: Experienced Painter Advice Needed
 

Paint forensics guy here. Frank is correct. Technical term used by most paint manufacturers is "rail dust". Happens when autos are shipped by rail. As the term implies, particles of metal from the train track falls on the paint surface and then rust, which burns into the finish plus creates the oxide color. Metal sparks from grinding does the same thing. Frank could be right however, more information is necessary since there are other paint defects that look similar but have other causes. Important to know if the finish is original or a refinish. If refinish, what type of prep was done? what type of undercoats; 1K or 2K? wet sanded or dry sanded? lacquer finish, enamel, or urethane? Single stage or clearcoat? The defect could be caused from the top down or the bottom up.

Re: Experienced Painter Advice Needed
 

One common issue for older refinishes: If lacquer primer was used (especially applied over non-treated bare metal - lacquer primer surfacer is porous) and then wet sanded before being painted, trapped moisture accumulates under the finish and forms circular "pin head" size blisters (1/32 to 1/16th inch diameter). Moisture cannot evaporate through the finish so it pushes the finish away. Over time the finish de-laminates at those pin head circles. The lacquer primer is then exposed to the elements allowing moisture to penetrate down to the un-treated bare metal; rust then begins to form. If the primer color is red oxide, it looks like rust at the beginning. Gray colored primer will do the same but not be as obvious until rust forms. Lacquer primer can also retain moisture by way of very humid compressed air when applied. Pin head blisters can form even though the primer was not wet sanded. Since there is some damage on a vertical panel (lower rear body panel), "rail dust" is less likely to be a cause.

Re: Experienced Painter Advice Needed
 

Can't get a good enough pic but the aforementioned points sound feasible.
I need a good SLR digital camera, friend has one and that should do what I need.
How disappointing the paint is, I think I'll just let it alone till I can't stand it and just refinish the roof.

Re: Experienced Painter Advice Needed
 

That's how I pick my next to-do project.