Hardened MAE over MAE?

Rick from NC · May 28, 2009

Stripped my Ford 4400 down in the fall. Painted the chassis with MP170 & unhardened MAE in late October. Worked on the sheet metal through the winter and have it primed w/ MP170 & MP281 surfacer. (yes I work really slow) I decided to bite the bullet and buy a supplied air system so I could use hardner on the sheet metal and upgrade to 2k surfacer/MTK on future projects. I know I risk lifting but I'm considering shooting several coats of hardened MAE over the unhardened MAE I shot on the chassis last October. My main question is how long will it take for lifting to occur? If I do a test area should I wait a couple of days?, a week?, a month? before knowing the result. The main reason I want a hardened topcoat on the chassis is for resistance to gas & oil spills but I also want to change the color a little. I painted the chassis with PPG code 12908 which is actually Equipment Dark Blue instead of 12809 that I intended to use which is Tractor Blue. Don't ask how I screwed that up. I'm still not sure myself.

GlenIdaho · May 29, 2009

Hello Rick;

Since no one has been able to get to your question, I'll offer my 2 cents. You should not have to worry about painting MAE with hardner over MAE. Since it has been so long since you painted the first time, it should be cured. You should scuff the paint with a 3M pad, wash with clear water, dry and then follow with a good wax/grease remover.

RandyB(MI) · May 29, 2009

I agree with Glen , it shouldn't lift now. If you wanted to try a spot , it should lift within an hour if it is going to at all. I would just go ahead with it. The only way it might still lift after this much time is if you had just dumped on the paint and had 8-10 mils on there , then it might not be cured all the way down. If you only put on the usual 2-3 coats , then it should be good to go. Don't sand it , scotchbrite it like he said and don't sand through to metal as you might to get rid of a scratch or something , because that will leave an exposed raw edge that MIGHT not be cured and that is where it will lift easiest.

Rick from NC · May 30, 2009

Thanks for the replies Glen & B. What about shooting MTK acrylic urethane over the unhardened MAE? Would the MTK bond to the MAE (assuming there's no lifting) or are the chemistries too different?

GlenIdaho · May 30, 2009

Rick;

I still think you would be okay if the existing MAE is cured, which sounds like it is. The bond would be mechanicl rather than chemical such when using Omni Epoxy which needs the top coat applied within 72 hours to insure the chemical bond. The mechanical bonding surface is created when you scuff the existing paint. The tiny scratches give something for the paint to grab a hold of. Try a small piece first and see how it works. If I'm incorrect perhaps B, Glennster, Rod, CNKS or another can straighten us out.

Rick from NC · Jun 9, 2009

Painted the chassis over the weekend. I think it turned out pretty good. I used my new breathe-cool supplied air system w/ the tyvek hood. The color is ppg code 12809 the label also says Ford OEM codes M1639A, M2J1639A, MX700501, & WT8050. I used MH101 hardner, and MR187 slow reducer. It was pushing 90 degrees. No signs of lifting or wrinkling so the 8 month old unhardened MAE must have been pretty well cured. I scuffed the paint with the maroon scotchbrite pads as recommended. Thanks for the help guys.

glennster · Jun 9, 2009

wow!!! looks great, cant wait to see it all done!!! what ya dont see is the countless hours of work that goes into a project like that. great job!!

Hardened MAE over MAE?

Rick from NC

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GlenIdaho

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RandyB(MI)

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Rick from NC

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GlenIdaho

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Rick from NC

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glennster

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