sealer really needed

M

moparmusclecars

I see many out there think if you have sanded the 2k primer nicely, that there is never a need to use a sealer before applying your color coat. What is the advantages or disadvantages of not using a sealer? I mentioned I always spray down a sealer coat, and some told me i was wasting my money, that it is not needed, and not necessary.
 
Here's one response from one know it all. "all the manufacturers will tell you, the best paint job you can do is sand the primer proper then paint. I have been Certified in every paint line in America. Seal new parts, bumpers or blend panels. Save your time and money, sealer will shrink and cause peel"

here was his second statement: I was a Sikkens tech Rep for years, please check with your rep. i'm telling you the best way to achieve gloss retention and color hold out. I want to help people make more money, save time too. just trying to save you money and time. sandpaper costs maybe 50cents a sheet, sealer 20.00 - 25.00 bucks to mix, then wait to dry, clean your gun..etc
 
I personally have done and still do both. On collision work I usually paint directly over the 2K, due to that fact that I am usually doing a blend and it would be kind of hard to seal 4 or 5 spots without getting overspray on the surrounding area that I need to blend the base into. Now on the other hand, on restorations, which is most of my work, I only use epoxy primer from bare metal to paint, so I use a reduced coat of epoxy as a sealer more for adhesion than anything. I have done a few cheap (relatively speaking) all over jobs that I painted directly over SPI 2K and have not had any problems doing so. As for sealer shrinking and causing problems, using a quality product such as SPI sealer will solve that worry. Most of the problems I have seen in the paint world come from using cheap secondary lines trying to save a dollar or from painter error (Heaven forbid any of us admit we may have mixed something wrong lol)
 
Sealer is used mainly to stop any bleed through from any bodywork that has been done. Also it is used to help address low hiding colors by using a sealer that is close to the color you are spraying you can save a number of coats of color saving time and money. Then you have the adhesion issue, color will adhere better to a fresh coat of sealer then by sanding alone.

On the other side of the coin is if you use a top quality primer either Epoxy or top self 2k (Epoxy being best) (all SPI too) after all bodywork then applying a sealer (unless using it for low hiding colors) would not be needed IMO, so long as the last pass of primer hasn't aged too long (like a couple weeks) adhesion will not be an issue and you could feel safe to proceed with paint. The downside to applying a seal coat is that is just one more chance for something to go wrong dirt, runs etc what your sealer looks like and whatever lands in it will transfer through the color and clear and no amount of wetsanding and buffing will get rid of it because it is under the color. I feel that the less time you spend in the booth you will be less likely to have a problem.

If you do your final prime (especally with Epoxy) in the color that helps best with low hiding colors then final sand, mask and paint inside of the Epoxies 7day window what would the benefit be for doing a seal coat? None IMO there would be no real need for it unless you want to, which would be fine also.

The choice is yours, wait too long before paint then it would be best to do one of the following, use either a seal coat,then paint and risk a problem or coat, sand then paint. Either way is fine
 
Urethane sealers are good for an even color and handling scratches that you missed, if coated in right time frame perhaps they give a little extra chip resistance.
My personal feeling is if primer sanded right and its an insurance job, no big deal either way.

Epoxy as a sealer is the best of best, I know of no restoration or rod building shop that don't use it as they have to live with these high dollar jobs.


For 15-18 years one of my jobbers has sold and insurance shop, he is direct with 9 insurance companies and has 4 painters, he will not take a car over 5 years old and the insurance companies love him as like he says, they never get a complaint.

Ten or so years ago, he asked me to come buy as certain cars would get chipped up in the front end if they drove gravel roads or expressways everyday.
My answer was to stop this, use epoxy as a sealer, now that is a real problem time wise in a shop like this but he took me at my word.
It stopped the problem! Hands down!

Then about 3-6 months ago he called said I have had three cars come back chipping, I asked with epoxy sealer? He said no, these were real rush jobs, I said any come back with the epoxy as a sealer, he said no.
I said well guess we know the answer, he said yea, just need to bitch at someone. LOL

So bottom line is if the car is just a used car special or just want it the same color, save money and base over primer.
If car is something to be proud of and want to last use epoxy.
 
Barry when you say if urethane sealers (reduced SPI epoxy) is sprayed in the recoat window, it may increase chip resistance. So how about when the window has closed and you scuff the surface? Still the same chip resistance? Im trying to figure out if a chemical bond inside the window is better than a mechanical bond outside the window.
 
No, I speak of Urethane sealers like SPI's #6400 series, urethane sealers are good but made for speed. Epoxy is totally different ball game.
 
I like using the Epoxy sealer on a overall or something I am spaying complete, such as a full side of a vehicle, I really feel like you get better adhesion.
However that's hard to do on collision jobs because of blending issues.
 
Ok, I have to get reduced SPI Epoxy out of my head as a sealer. It can be used as a sealer, but its not technically a sealer. Please correct me if I am wrong.
 
Sealer really amounts to a reduced primer. Let's use for example Nason (it's crap I know) 2k urathane primer then you buy Nasons 2k sealer to seal just before paint. It is the same exact material, the sealer is just heavely reduced from Nason and sold as a sealer and people buy it.
Now as for sealing when you need to blend I always do a quick mask of the adjacent blend panels to keep any overspray off them then unmask when ready to start the color coats. If I need to stay inside the same panel for the repair and paint I put the car in the booth with the larger blend area further away from the fan and keep the guns fan pattern and air pressure as low as possible to keep it where I need it and haven't had any problems with overspray sticking where it shouldn't.
As Barry said Epoxy is the best at everything adhesion, hold out, stopping bleed through and chip resistance. The down fall is time if you are under the gun to get something out (insurance, unruly customer etc) you would be better served using another product such as a reduced 2k (SPI) or going straight to paint after final prep as long as the last prime window has not expired.
 
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