Lighting Anyone seen powder coat coming off passive heat sinks?

[Ozone69]

Just noticed a day or two ago that the black powder coating on two of the passive heat sinks in my light rig appears to be coming off (if not mostly gone at this point). I can't say how long it's been happening, because I just noticed it, but I would guess a little while with how far gone they are. They don't feel any hotter then they other two or read noticeably different with an IR temp gun. I try to keep a lot of light air movement in the closet, so there is some good air flow over things. I hooked up the Kill-A-Watt meter this AM to double check, and the fixture is still pulling the same 223 watts it has always used at the wall.

From a functionality point of view, I don't know that I'm all that concerned because it shouldn't really affect the heat sink's ability to do it's job. Just mostly curious why it might have happened and if it's a semi-common thing with these heat sinks or not.

Hard to see in the overall shot, but it's happened with both the outer heat sinks:

Closer shot of the one on the far right:

 

[Autobeast]

Just noticed a day or two ago that the black powder coating on two of the passive heat sinks in my light rig appears to be coming off (if not mostly gone at this point). I can't say how long it's been happening, because I just noticed it, but I would guess a little while with how far gone they are. They don't feel any hotter then they other two or read noticeably different with an IR temp gun. I try to keep a lot of light air movement in the closet, so there is some good air flow over things. I hooked up the Kill-A-Watt meter this AM to double check, and the fixture is still pulling the same 223 watts it has always used at the wall.

From a functionality point of view, I don't know that I'm all that concerned because it shouldn't really affect the heat sink's ability to do it's job. Just mostly curious why it might have happened and if it's a semi-common thing with these heat sinks or not.

Hard to see in the overall shot, but it's happened with both the outer heat sinks:
View attachment 815103

Closer shot of the one on the far right:
View attachment 815102

What cobs are they what company?

 

[wwwillie]

HMMmm... Thought they were anodized not coated. There's dust or something, I can see a finger print in it. Overspray of some sort?
Have yet to see anything like that on mine. Mine are Mechatronix.

 

[Ozone69]

What cobs are they what company?

Think the company was called Pacific Light Concepts. They don't sell just the pieces anymore, but used to sell COB's, holders, heatsinks, etc..etc..

Dug up the parts list from my old build thread, here's the run down:

4x Cree CXB 3590 3500K CD 36V COB
4x PLC 140mm Anodized Pin Heatsink
4x Ideal Chip lok holder and reflector adapters
4x Ledil Angelina Reflectors
LSD Power 200w Driver 1.4amp/145v

 

[Ozone69]

Another thought...I did drill holes in the edges to accommodate the cable hangers. So maybe something around the coating flaking off starting at where I drilled as a theory? Long shot, but just brainstorming. Could see maybe some current in the heat sink, but would think the heat sink would have to be waaay noticeably hotter than the other two to get into a temp range for the paint to start cooking off, so not sure on that enough to want to tear into things. Did double check that the hanger wire hadn't cut through the wire insulation after looking at the pic I posted, and insulation on the wires is all intact.

 

[wwwillie]

Dude, pretty sure they are anodized and not powder coated. I had thought so and the parts list confirmed it.
4x PLC 140mm Anodized Pin Heatsink

Check out this https://www.finishing.com/2400-2599/2459.shtml link. It has info on staining of anodized aluminium. It seems to match what you are seeing although I did not read too much of it.

 

[BigSm0]

It’s not a big deal as far as performance goes. The anodization does help with cooling but it’s minimal. The reason why would be my only concern.

 

[L0wbob2017]

Another thought...I did drill holes in the edges to accommodate the cable hangers. So maybe something around the coating flaking off starting at where I drilled as a theory? Long shot, but just brainstorming. Could see maybe some current in the heat sink, but would think the heat sink would have to be waaay noticeably hotter than the other two to get into a temp range for the paint to start cooking off, so not sure on that enough to want to tear into things. Did double check that the hanger wire hadn't cut through the wire insulation after looking at the pic I posted, and insulation on the wires is all intact.

yep, you killed the coating with drilling holes. In that moment it isnt sealed anymore and ions can change layers. This is killing the coating. Another thing that adds on this is that the warmer the material now gets, the faster these ions can move.

So as a result the complete coating will peel off as a form of "dust". Now depending on how much relative humidity u have, the heatsink will corrode more or less fast.
Thats the reason why the coating must be complete sealed so nothing can react with the metal from the heatsink.

 

[wwwillie]

yep, you killed the coating with drilling holes. In that moment it isnt sealed anymore and ions can change layers. This is killing the coating. Another thing that adds on this is that the warmer the material now gets, the faster these ions can move.

So as a result the complete coating will peel off as a form of "dust". Now depending on how much relative humidity u have, the heatsink will corrode more or less fast.
Thats the reason why the coating must be complete sealed so nothing can react with the metal from the heatsink.

I could understand that if it was coated but it is not from what I see.

 

[L0wbob2017]

I could understand that if it was coated but it is not from what I see.

the part said "anodized". this means the top layer of atoms will create a oxidlayer that works like a coating.

Wikipedia:
"Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts."

https://en.wikipedia.org/wiki/Anodizing

so once the layer is thick enough nothing can react with the metal, but the drilling killed the layer and the chain reaction began.