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JT56
04-15-2013, 05:10 PM
Let me start I am not a body man so looking for advise. My dad broke a couple of horses for guy and he painted this car with Imron back in 1980. I started noticing some cracks on the back deck lid. This past weekend a piece came off. This car has been parked in a garage since 1980. Has seen water only when cleaning it and been in the rain a total of 5 times since 1980. Can anyone tell me if this is bondo, lead or what? I want to repaint the car after the mini tub, but needing some opinions from experts one what to do. Do I take it down to the metal or not. I have had both responses from local paint shops. Thanks Guys. Gals welcome too.

Joey

JT56
04-15-2013, 05:11 PM
Let me start I am not a body man so looking for advise. My dad broke a couple of horses for guy and he painted this car with Imron back in 1980. I started noticing some cracks on the back deck lid. This past weekend a piece came off. This car has been parked in a garage since 1980. Has seen water only when cleaning it and been in the rain a total of 5 times since 1980. Can anyone tell me if this is bondo, lead or what? I want to repaint the car after the mini tub, but needing some opinions from experts one what to do. Do I take it down to the metal or not. I have had both responses from local paint shops. Thanks Guys. Gals welcome too.

Joey

Sorry forgot to upload pics

NickP
04-15-2013, 05:53 PM
Get it naked.

chevynut
04-15-2013, 06:02 PM
Looks to me like what caused the problem is paint underneath the new paint. I would take it to metal. Imron was one of the very first urethane paints. I remember seeing it used in 1973 when I was in aircraft mechanic's school. It was brand new around that time and a local guy painted his homebuilt airplane with it.

Rick_L
04-15-2013, 06:13 PM
I agree, the problem looks like it's either rust or a failed repair under the paint. It could easily be a bondo filled rust repair, and if it is you have proof it won't last. It has to go to bare metal in that area, and probably needs to everywhere. Then repair any flaws with new metal.

As said, Imron was one of the first commercial urethane paints. It's actually "polyurethane", whatever that means. One thing it means is that the paint is hard as a rock, and it doesn't flex. It's still used as an industrial paint, mostly on airplanes and trucks - which always was the primary use. Go back with an automotive urethane paint, it's easier to color sand and polish to make it look nice.

JT56
04-15-2013, 06:20 PM
What is the best method to get back to metal?

Rick_L
04-15-2013, 06:22 PM
Anything that doesn't warp the metal or leave chemical residue that's not neutralized.

chevynut
04-15-2013, 10:05 PM
Most automotive paint today is acrylic urethane. Imron is polyurethane. Here's something I found....

Polyurethane vs. Acrylic Urethane Finish









Polyurethane and acrylic urethane finishes come in two-part epoxy formulations. Polyurethane also comes in single-part oil-based formulations, while acrylic urethanes do not. Acrylic urethanes have many advantages, but with these advantages come trade-offs.





Strength

In general, polyester urethane (polyurethane) is stronger than acrylic and better resists chemicals, abrasions, stains and substances like liquor. More flexible than the stiffer acrylic, polyurethane resist chipping and movement stresses. New, more powerful acrylic urethanes on the industrial market resist abrasion and wear almost as well as polyurethane, but these have been slow to come to the general public and as of May 2010 were available only to professionals in the auto, flooringhttp://images.intellitxt.com/ast/adTypes/icon1.png (http://www.trifivechevys.com/#), construction and manufacturing industries.



Drying Time

Polyurethane finishes take longer to dry than acrylic urethanes. Various brands of each type have different dry and cure times, but acrylic-based finishes set and cure more quickly. Some acrylic formulas dry to the touch in under 10 minutes. Faster drying speeds applicationhttp://images.intellitxt.com/ast/adTypes/icon1.png (http://www.trifivechevys.com/#) dramatically, but can make water-based urethanes trickier to apply successfully.








Application

Both polyurethane and acrylic urethane may be sprayed on. Brush application of two-part urethanes of either type requires a quick, practiced hand. Acrylic urethane, particularly, gels so quickly after being spread that after two or three brush strokes, you won't be able to continue working on a spot without leaving obvious brush marks. Acrylics must be sprayed on boat hulls and furniture where a smooth surface is essential. Polyurethanes are more forgiving when brushing or rolling. Both types require at least two thin coats to ensure adequate coverage.



Coating

Polyurethanes typically cover more square footage per gallon than acrylic counterparts. Most polyurethanes are harder to buff to a shine than acrylic-based products, though newer polyester resins have made some polyurethanes easier to buff.



Adhesion

The more flexibile polyurethanes adhere to surfaces better than acrylics, although both have problems with adhesion. Both are frequently applied over an epoxy primer or have epoxy formulas. Epoxy primers prime the surface and level out imperfections, bumps and ridges that high-gloss urethanes tend to highlight.



Cost

Acrylic urethanes are more expensive than polyurethanes, more complicated to apply and easier to mess up. Two-part polyurethanes are more expensive than one-part varieties. Brands vary considerably in cost, durability and performance. Acrylic urethanes vary most widely from brand to brand, with some performing as well as polyurethanes and others not doing nearly as well.



Ultraviolet Light Resistance

Polyurethane clear-coats tend to yellow over time when exposed to UV light--more so than acrylics. Ultraviolet light (UV) breaks down finishes and the surfaces beneath them. Expensive additiveshttp://images.intellitxt.com/ast/adTypes/icon1.png (http://www.trifivechevys.com/#) can help improve UV protection to underlying surfaces for both polyurethane and acrylic urethane coatings and a few high-end acrylic urethanes come with UV protectants included.







Read more: Polyurethane vs. Acrylic Urethane Finish | eHow.com (http://www.ehow.com/about_6504500_polyurethane-vs_-acrylic-urethane-finish.html#ixzz2QbEfJf8W) http://www.ehow.com/about_6504500_polyurethane-vs_-acrylic-urethane-finish.html#ixzz2QbEfJf8W

Rick_L
04-16-2013, 07:48 AM
I don't know the background of the author or the lingo of automotive paint chemists.

I do know this. In industry, there are two types of polyurethane thermoplastics - polyester based and polyether based. So to say that polyurethane is polyester based is not correct in that context, just that it could be. Also, polyester based polyurethanes do not hold up well when exposed to water.

Also polyurethanes are not epoxies. Two different things.

Perhaps the world of urethane and polyurethane thermosets is different from thermoplastics, and some of the terminology is smeared, but I doubt it.


the above gives me some doubt as to the credibility of the whole article.

JT56
04-16-2013, 08:56 PM
After reading Chevynut post; so the polyurethane would be good base? Does anybody know how much money it adds to remove back to metal? I would remove trim and interior ect...

chevynut
04-17-2013, 07:27 AM
IMO the best way to get it back to metal would be media blasting. It's not cheap, probably $1000 for the whole car. I wouldn't use the Imron as the base, because it obviously has a poor base under it as evidenced by the cracking and peeling. IMO you'd just be wasting money painting over it.

Rick_L
04-17-2013, 05:18 PM
A fellow who doesn't post here reminded me that stripping Imron paint puts isocyanate compounds in the air, with some of the same hazards as spraying them. So breathing protection is needed. Obviously you'd need that if blasting, no matter the media used. But you'd need it if sanding also.

chevynut
04-18-2013, 05:18 AM
I don't think that's true Rick. I believe the isocyanates are reacted with other chemicals on curing and aren't free in the cured paint. But I haven't researched it either.

Rick_L
04-18-2013, 08:09 AM
I wondered that myself about the time I finished posting. There has been a chemical reaction as the paint cures. So you may be right.

Still, if you are doing heavy sanding, it doesn't really matter what the dust is, it's not good to breathe large quantities of it.

Rick_L
04-18-2013, 06:25 PM
My mystery source came back with some MSDS sheet recommendations and discussion. The MSDS recommended a particulate filter when sanding. I'd guess any automotive paint would have the same recommendation. If nothing else there's a difference between vapor (spraying) and particulates (sanding or blasting).

JT56
04-19-2013, 05:11 PM
Thanks for all the feedback!