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Is automotive paint porous or non-porous?
a.k.a. Patrick
08-24-2005, 09:15 PM
Oh this will be interesting..............
Im going to be the first and take a stab. Its my belief (Maybe Im straying here) a vehicles surface is somewhat porous.......
Ah, come on Patrick, what ya think?
Patrick, you brave soul. The reason I posted this is I`ve heard arguements from both sides.
papi_jay
08-24-2005, 10:15 PM
When paint is fresh it is non-porous as the film that forms on top of it " floats " as the paint gasses out for 60-90 days after paint is applied and flashed .
Then > supposedly as time goes on , paint becomes more porous after paint is done gassing out > paint goes thru different temp and seasonal changes > different contaminents embed themselves > chemicals make contact and > nature in general including birdies and such .
Being that I used to do custom auto painting for a living though I know of 3 methods that leave the paint as non-porous as possible IF using the right final coat as well ....
1.) Properly laying more than 1-2 coats of clear at proper flash ( and being quality clear w/proper hardeners ) and having UV hardener mixed in an being an EXTREMELY UV stable / Uv/UB resistant clear ..
2.) UV curing , not heat curing . UV curing dries the paint from the metal outwards , heat is kind of like slapping it around and telling it to harden cause you said so . Most heat booths are downdraft also .. nm ..
3.) A final flow coat over the last and final clear coat . Flow coat is simply a heavily over reduced final clear coat . Usually the paint cup is filled with up to 60-75% reducer , final clear coat is flashed twice as long as required and the over reduced clear is sprayed on and is EXTREMELY smooth and glass like .
The paint has to be kept in a safe dust free environment though longer than normal after uv curing to ensure it settles properly . Then it is cut , buffed and polished and glazed with body shop safe products such as 3m`s perfect-it III and Imperial line before delivered to customer .
That final flow coat won`t open up much ever if done right , but of course clay should still be used after 1st year if it is a daily driver in the city etc ..
Come to think of it Po85RD would be a perfect final polish for flow coats , but no one knew about it back then ..
foxtrapper
08-25-2005, 06:17 AM
For all intents and purposes, automotive paint is non-porous. Automotive primers are highly porous though.
The statement of the paint being non-porous has limitations. The first is with regards to what. It often times is absorbent of petroleum solvents. It is not that it is porous in the sense of flowing through it like a window screen. But since it will absorb, it will spread thoughout, eventually traveling through to the back. This is a slow process.
Even slower is water. Constant submersion will allow a minute quantity of water to transmit through. This is well known in the boating world, but has very little direct application to the automotive world, as we don`t park our vehicles under water.
Quality of the paint and application has a substantial influence on the waterproofness of the paint. The classic example we are all familiar with is rattle can painting something and having it promptly start rusting through the paint when left outside. This is not a case of water getting in through the edges, but directly through the paint surface.