Centari is available in three different field mixes:1. Centari w/Ultra Performance Pak - This is an acrylic enamel that DuPont actually refers to as an acrylic urethane - There are isos in the activator that needs to be used with this formulation. 2. Centari w/Hardener - This is the conventional hardened acrylic enamel. There are isos in the hardener that needs to be used with this formulation. 3. Centari w/Uktra 1K Pak - This is a non-hardened acrylic enamel that does not have any isos in any of the required ingredients. This is the one you want if you want to avoid isos. The tech sheet indicates that it may be recoated anytime after 4 hours, but I have never tried it. I've used both #1 and #2 above but not the 1K Pac. Yes, I agree, the epoxy primer such as the PPG OMNI MP170 is an excellent primer. It doesn't get any better than an epoxy primer for bare metal, in my opinion. The 182 surfacer is a urethane product that requires an iso-containing hardener. The 181 is a lacquer-based product that does not require a hardener and is iso-free. Both are relatively fast dry but the 182 dries initially by evaporation and then cures by chemical reaction of the components. The chemical reaction is due to the presence of the hardener.The 181 doesn't rely on any chemical reaction and doesn't "cure" in that sense. It only dries by evaporation of solvents in the product. The problem that exists with the 181 that doesn't with the 182 is the possible re-emergence of sandscratches after application of the topcoat. Since the 181 doesn't cure, it is susceptable to possible re-liquification upon being exposed to solvents in the topcoat. Should the 181 be applied too dry (easy to do) it can bridge over sandscratches. After sanding and applying the topcoat, the 181 can possibly re-liquify and settle back into the sandscratches, causing them to ultimately show through the topcoat. Furthermore, if it's applied too wet, the bottom portion of the film may not be completely dry, even if the surface indicates it is. In that situation, if a topcoat is applied too soon, the 181 continues to dry and shrinks into the sandscratches, causing them to show through the topcoat. The only advantage that I see in any lacquer-based surfacer is that it is iso-free. And that's only an advantage to those w/o safe breathing equipment. The use of this type of surfacer has been almost completely replaced by urethane surfacers such as the 182 for most work nowadays. Lacquer-based products are also getting squeezed hard in some areas due to air emissions. In my area, if you buy any of the 181, you are forced to buy a gallon of MS250, a thinner based on acetone, an exempt solvent - whether you need it or not. You cannot buy just the 181 alone. Lacquer thinner could be used with the 181 but that is discouraged by air emission regulations. The Centari is a true acrylic enamel, even in the non-iso mix. If I understand correctly, the IH2150 is an acrylic-modified alkyd enamel. While it can generally be said that an acrylic enamel is "better" than an alkyd enamel, the "acylic-modifed" hybrid tends to blur the differences. Since I have never used the IH2150, I cannot say if the Centari is truly better. It may be, but only marginally so. It does have a very long history as an excellent paint. The last time I used any was a few years ago with the #1 mix formulation above. I was very satisfied with that. I do know that Centari is now quite expensive for what it is so I would expect it to cost significantly more than the 2150. Availability of color shade match to the 2150 is also an unknown, I think. If you have trouble with a good match, you could try having a fresh 2150 application scanned and compared with DuPont's generic "SpectraMaster" colors. As far as I know, all those colors are all available in Centari. Check with your local DuPont jobber if you want to find out more. I don't think it will help you out at all with your scratch/nick issue though. Rod
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