Question for Joe Holihan (automotive)

[RAM]

Hey Spock:

Your paint peeling problem was very common with 90's vehicles. some manufacturers back then, to cut costs, skipped a primer process in the factory causing the paint and/or the clear coatto peel, mostly on the panels that got the biggest UV exposure. Your condition is called "Paint Delamination". At one time I worked in an area that went after these manufacturers for this product liability issue, but since it wasn't safety related, it was difficult.

I think there were numerous TSB's (technical service bulletins from the manufacturer) on that problem. If I find any I'll PM you the numbers.

[spock8113]

thanks, RAM,
I was looking at it the other day and parts of the primer look gray and parts of it look olive drab? Seems "bright white" has this problem more than other Chrysler colors.
Delamination sounds spot on.

[kzang]

That delamination never happened on my 1993 van. But I've seen it on vans all the time, right under the rear window. The paint just peels off, and there isn't any rust underneath it.

I believe that in my case, the water went down the glass into the door....but then why was there a problem with the undercarriage rusting. I never could open my windows if there was the slightest freeze. They would be frozen shut.

But everything in the door worked fine???

Thanks for the explanation about paint and undercoating Ram and Spock. I'm not moving to Phoenix though! The summers there can melt the rubber gaskets.

Kathy

[Apruesing]

Anytime someone starts talking about paint it peaks my interest. Paint can delaminate or peel for many of the reasons already explained. When it just peals off with no rusting under it, it can any of a multitude of causes. One of the main reasons primers are used in almost any application is to improve adhesion. Steel may feel smooth, but it is actually very rough even when sanded "smooth" there are peaks and valleys in the steel that you can see under magnification (sometimes with the naked eye). When a coating bonds to the surface of anything there are two main typed of adhesion that can take place. Mechanical Adhesion is a process where the coating "grips" those peaks and valleys in the substrate causing the paint to hold onto the surface during and after film formation. If the surface is too "smooth" (not enough difference in the peaks and valleys, it will not be a strong mechanical bond, and the paint can and will fall off. If the surface profile is too great (too much difference in the peaks and valleys) you end up with what is called pinpoint rusting. The surface of the steel actually sticks up above the surface of the film and will start rusting. The other major type of bonding is called a chemical bond. There is a chemical reaction that takes place that chemically bonds the two materials together (substrate and coating). Primers are often used, among other reasons, to improve adhesion, help prevent corrosion (rust), and on vehicles to lend more flexibility to the coating.

Typically The harder a coating is the less flexible it is. The more flexible it is the "softer" it is. Auto primers are "softer" than the topcoats to help provide a "buffer" between the steel and the topcoat. For example the hood of a car can get quite hot, even in the winter. The steel can heat up rapidly which causes it to expand, when it cools off it will contract. The top coat will heat up but not as quickly as the steel and it too expands and contracts but at a different rate than the steel. This causes problems with a coating that needs to be durable yet flexible, that can take a hit from a rock or a bug when driving 70 MPH but can expand and contract with the rapid heating and cooling cycle that happens to it many times a day. Thus primers with more elastomeric properties are used to help the coating remain flexible while still durable. That is one of the main reasons oil based coating crack as the coating gets older. Oil based coatings cure as a result of contact with air. The air oxides the coating and cures it. The actually never stop curing. They become harder and harder with age and eventually will crack and the coating hardens, shrinks and rips the film apart.

Also someone mentioned salt. Salt+Paint=Bad. Salt not only speed up the corrosion process by making the electrolyte (water) more conductive, and corrosion being an electrochemical process will make it MUCH quicker. Also if it finds its way under the coating it will cause osmotic blistering where the salt will draw water through the coating causing blisters (bubbles) that can fill with water, popping the paint off and creating a nice environment for corrosion.

Just thought i'd throw my $.02 in.

[east1952]

Several months ago I had a close call while driving on the interstate in VA. A piece of truck tire came flying across my lane and hit the grill on the front of my car. It (the grill) gave a little but appeared to stay in one piece. I noticed this week, however, that a section of it was neatly broken in two, but it's only noticeable when I press on it. My husband went to the auto parts store to find some kind of glue that would repair the grill, but after trying two different types, was not successful. To replace the grill would also mean replacing the bumper around it, at a cost of approximately $300. As for now it's only a cosmetic problem, but I'm still wondering if there is any kind of glue, epoxy, whatever, that would work. Any suggestions?

Thanks,
Liz

[RAM]

Liz, take you car to a reputable collision repair shop. It can be repaired but glue isn't the answer, at least not the kind you'll find at a hardware or auto parts store. It may to to be plastic welded. If the grill is the same color as thr car, it will need to be refinished as well.

[authement]

Hi Ram,

Do you know if plastic welding it difficult? I seen welding kits and it seems pretty basic. Looks like a good tool to have in the garage.

Authement

[RAM]

Auth, plastic welders look kind of like a cross between a soldering iron and a hot glue gun. The thing about plastic welding (at least in automotive) is that you have to use the same material that the part is made of. Each plastic or flexible automotive part should identify the type on the back side of the part. The filler stick (or plastic welding rod) has to be the same as the part or it will not work. After plastic welding, the part will still need to be sanded and finished with a synthetic body filler before priming and painting.

[Byron]

If it's a hard plastic grille, then a plastic welder won't do the job; they were designed to repair car bumper covers (which is a soft plastic). I'd try Loctite Super Glue first. Just make sure the affected area is clean and the break area is sanded a bit (the "profiling" that sanding creates insures that there is an uneven surface for the glue to stick to).

[Dr. Meyer]

Submitter Question: I'm considering taking more schooling. I've completed training but my question is do you think one can learn as much in the field working as they can taking additional classes? I am a hands on type of guy and Im not sure if employers expect guys to know everything up front. I'm good at starting at the bottom, I just dont want to stay there forever. Thanks.

Answer:This is an age old question..more school or hands on?.The path I chose was hands on. no formal training. Just learned as I went. But this had a cost. I stayed at the bottom of the pay scale for a couple of years until I started taking and passing ASE test in my current field leading up to a Master status. Also what I found out is not a lot of companies will not hire a tech fresh out of school, they want experience and they want you to have a complete set of tools. Which takes years to collect/ and money. As for knowing everything no, but don't make mistakes this leds to comebacks and reputation. If you don't know how to do a particular job don't stare at it...ask. Most larger companies will give a fresh tech a chance, because they might have a seasoned person willing to guide them or teach them. It is at the interview where you can ask.

I will give you an example; the company I work for hires techs out of school and talking to them they applied at a number of different places before they were giving a shot.

Good luck