Paint thickness integrity difference between multiple coats and single coat
Paint thickness integrity difference between multiple coats and single coat
(OP)
Hi everyone,
To build up a thickness of 600 um we are applying 3 coats of 200 um of the same paint material, I suppose it's to avoid sagging during application but when on the first coat we achieve a thickness over the spec the client ask to sand down. I'm wondering if we achieve 600 um with a single coat if the integrity of the paint would be any different than with 3 coats, would we get cohesion failure on a pull-off test?
To build up a thickness of 600 um we are applying 3 coats of 200 um of the same paint material, I suppose it's to avoid sagging during application but when on the first coat we achieve a thickness over the spec the client ask to sand down. I'm wondering if we achieve 600 um with a single coat if the integrity of the paint would be any different than with 3 coats, would we get cohesion failure on a pull-off test?
RE: Paint thickness integrity difference between multiple coats and single coat
http://offers.exova.com/paints-and-coatings-failur...
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Paint thickness integrity difference between multiple coats and single coat
RE: Paint thickness integrity difference between multiple coats and single coat
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Paint thickness integrity difference between multiple coats and single coat
My guess would be that we could get cohesion failure and that the integrity would be altered during curing.
but how does the curing is any different when it's overcoated the following day? as full curing is around a week in this specific case.
Why to sand down and the next day build up again?
RE: Paint thickness integrity difference between multiple coats and single coat
SSPC PA2:
Correcting for Low or High Thickness: The specifier should specifically state the methodology to correct the applied and cured film for low or high thickness. If this information is not contained in the specification, then the coating manufacturer’s instructions should be followed.
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Paint thickness integrity difference between multiple coats and single coat
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Paint thickness integrity difference between multiple coats and single coat
If the spec require 3 coats when it's apparently possible to apply it in one layer or 2 then there is certainly a reason, so far I thought it would mainly be to avoid sagging.
RE: Paint thickness integrity difference between multiple coats and single coat
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: Paint thickness integrity difference between multiple coats and single coat
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Paint thickness integrity difference between multiple coats and single coat
Alkyd paints cure by reaction with oxygen. Thick coats will not fully cure and will skin over and wrinkle.
Water based paints require that the water evaporate before the coalescing solvent does. A thick coat will trap water in the coating preventing the resin particles from coalescing.
Surface tension helps to level and smooth coatings. Thick coating will experience variations in solvent and surfactant concentration during the drying process, which will cause orange peel and other defects.
Gravity causes drips and says.
Paints shrink considerably during drying, which will result in defects in thick coating but not in thin coatings, such as mud cracking.
The science behind paints and coatings is quite complex and varied.