Originally posted by sevt_chevelle
Barry, Ive read in some of your past posts that paint companies are NOW wanting 80 grit for epoxy and 2K urethane primers.
What companies are doing this switch??
In the past the grit range has been around 150 to 240.
Ive been a big PPG fan for many years but now work at a shop using Dupont products. I do metal work but have to prime the work myself then send off to paint. We use 4609 or 4906, I believe.
I finish off the filler with 180 and feather edge the surrounding paint with 320
Body filler or 2K primers its not an issue.
I have changed my literature and I do know ***** is going to and one of the **** guys at the Radtec meeting said they were.
Reason is a letter was sent out by one of the epoxy resin company's about two months ago acknowledging some problems.
In short (I don't have letter here) i will try and sum up.
Metal coatings are changing such as high strength and different types of coating for rust protection from the OEM. What is happening is let say you sand with 180 the epoxy may not get into the finer scratches and adhesion is lost and corrosion protection is limited because of air trap-page that will lead to delamination.
Compounding this problem is the voc laws. The high solids resins add to the problem even more so than the finer scratches.
Also noted in the letter, it has been assumed in the past epoxy adhesion was 45-50% charge +/- as all items have a charge except things like TPO, TEO etc. Now they feel the charge rate is in the 35-45 % range.
Another problem (this is my opinion) is the so many different types of sand paper being used. The cheaper ones break down faster and if not changed enough the metal almost looks buffed with scratches.
There is no reason not to use 80, in past its been said on here that 80 is to rough but I have never (IN BARE METAL) seen an 80 scratch that was not covered with one coat of epoxy. Now in body filler or primer thats a different subject all together.
I deleted the names of the other company's as, really not my place to say, but you will see over next year different procedures being recommended.
What your using-go to 80!