Message Board Thread - "Delamination of coatings"

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Delamination of coatings Lex 7/16/2007
This will open up a box of worms I'm sure!

I had a chat with a prospective client regarding a thermographic survey of his electrical distribution system - no problem. He was also interested in how thermography could help in the identification of delamination of coatings on products being manufactured and coated on his site.

Prior to discussing with him further I would like to pick the brains of you good people on any experience or techniques used previously for this sort of work.

Information is limited at the moment - I can't tell you the coating material or the objects being coated (I shall add this when he is back from his holiday).

I am using a FLIR P640 and am a level 1 certified thermographer.



 
Re:Delamination of coatings Top Gun 7/17/2007
You will need to consider the chemistry of the material you are dealing with. Is it metallic or other, i.e. organic or silicon based? Organic and silicon materials are made of atomic lattices that are bonded together with covalent bonds. These materials tend to have higher emissivities. Metals tend to have low emissivities. To see delaminations you need to employ Active Infrared Procedure techniques where you need to add radiant heat to the surface for a short time and watch with the infrared camera how the heat soaks into the material. A delamination will "reflect" some of the heat back to the surface which you will see. Good luck!
 
Re:Delamination of coatings Top Gun 7/17/2007
Metallic materials will be much more difficult to evaluate since they are reflective and heat travels much faster through them. Here you will need to alter the surface by adding a spray-on powder or paint or very thin tape which will increase the emissivity. Then the radiant heat will doposit into the surface and travel into the material. Reaction times to shallow delaminations will be very short, so you will need to "play" with this for some time, adjusting intensity and duration of radiant heat.

The other type of materials (covalent) should be easier to work with and you should not need to alter the surface. Heat also travels more slowly through these materials. Good luck!
 
Re:Delamination of coatings mg 7/26/2007
As mentionned in the previous post, active thermography would be likely to work. Of course it depends on the coating properties and on its thickness...

Pulsed thermography is likely to be your best bet. There are a few good companies providing this kind of service. If you can't find them contact me...

marc.genest(at)nrc-cnrc.gc.ca

Marc
 


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