One of my customers called and informed me that an insurance agent declined to pay for priming or sealing new e-coated parts. The agent told my customer that sealing or priming new parts wasn’t a necessary step in a proper repair process. Anybody that knows me well will not be surprised to learn that I got very excited about this statement. How can someone in our industry make such an irresponsible statement? And then I leaned back and thought about this for a moment.
During the course of a year, I visit hundreds of shops and have witnessed this exact procedure performed more often than I cared to admit. By simply looking around our industry, an insurance agent that likely never had to repair a vehicle for a living could easily get the impression that sealing or priming new parts is an optional, but not a necessary step in a repair process. I feel comfortable about the fact that most, if not all major paint manufacturers will agree with me, painting directly over e-coat is not a recommended repair process. Furthermore, paint failure as a result of this practice would not be covered by most manufacturer’s warranties.
There are several problems with painting directly over e-coated parts. Although OEM e-coat is an excellent corrosion protection coating (not sure about some of the aftermarket parts), e-coat contains no UV protection package. E-coat is generally epoxy based and unless completely shielded from UV rays, its surface can become unstable. Resulting in paint layer separation and peeling. Some of the newbies in our industry may not remember the early 90’, but many of us do. How many GM and Chrysler factory paint peelers did you repair in your professional career? These cars and trucks peeled for the same reason, UV exposure to the e-coated surface.
If you repaired one of these vehicles, you likely remember that the surface of the vehicle was powdery after you peeled of the paint layer. This powdery subtends that easily rubbed off onto your fingers was the top layer of deteriorated e-coat.
Just put enough paint on it and you should be fine, right? I wish it were that easy. The first problem with this thought process is: how much is enough? Are you thinking 4, 5, or 6 coats of paint? Eight to 10 coats on some reds? The truth is that no one knows when full coverage is achieved during the paint process. Take a piece of glass and paint it with basecoat and clear. After it cured completely, hold it up to the sun and see if any light penetrates through.
Attempting this exercise will quickly demonstrate that this approach doesn’t work. It takes much more paint than anticipated before 100% coverage is achieved through basecoat application. Protecting the integrity of your work through sealing or priming instantly emerges as a more cost effective solution. And if cost wouldn’t be a factor, the resulting high film build of basecoat color would present a paint problem of its own.
The next issue with painting directly over e-coat is stone ship resistance. E-coat is a very hard coating. The difference in hardness between e-coat and basecoat is too great for a long lasting paint finish. The application of a primer or sealer to the e-coat will bridge this cap. Although there is no way of fully preventing rock chips from happening, a sealed or primed surface will outperform an e-coated surface after impact by a large margin.
The last point I like to make is the surface prep. E-coat is a hard surface and sanding it can be a workout. Ninety percent of shops will use a DA sander to prep the e-coated surface. If you don’t seal or prime the part, how do you know if you left enough e-coat behind for proper corrosion protection? Most e-coat layers are only 0.5 to 1 mil to start with. My observations suggest that 70% of all sanded e-coat surfaces display some level of transparency or bare metal surfaces. Unfortunately, I have seen people paint right over that too.
When asked why, the most frequent explanation I receive from shops that paint directly over e-coat is cycle time. Shops don’t feel that they can afford to give up the time to seal parts in the booth. While I appreciate the value of cycle time and booth hours, it is no excuse for painting directly over e-coat. Nobody says you have to do it as a part of your final paint work, in a matter of fact, I strongly advice against it. I propose sealing parts ahead of time, ideally as part of the cut-in process. Put one good coat of sealer on the outside of the part, let it flash off to a point that you can safely turn them over and cut-in the rest. All the shop has to do after hanging the part is giving the sealer a light scuff by hand for adhesion, clean and paint. This process allows the shop to maintain booth KPIs and put out a quality repair at the same time. As an added bonus, you will also improve coverage and color match as well.