Faded anodized heatsink

[Victoss]

I have 2 black anodized aluminum heatsinks from Rapid LED which are over a year old, while taking them off to add more for the new tank I see this weirdness going on. The right side in the pictures is usually the wetter side having a coat of skimmate on the outside from my HOB skimmer so I don't think it has to do with water (there is also splash guards placed on the heatsinks when in use). I know there has been a little stray current on the heatsinks, do you think that could be it? Lets just say I'm no physicist. Mind you that shadow in the second pic is not from the light, it's physically on the heatsink! ???

Thanks guys!

 

[AdamS]

Because of the pic on the right, where the colour change is localized around the LEDs, I would suggest it is heat. But i remember using annodized aluminum parts in race cars with no affects like that. Maybe the process that is used on Rapids heat sinks is not as good?

 

[Duke]

I'd say ur bang on.. Heat-related..  More like transparent spray painted than good anodizing, I wouldn't worry.. Aesthetically it would suck if you could see the lights tho

 

[Boga]

I would say that the dye in the heat sink discoloured. Poor anodizing process.

Possible causes:
- heat around the LED grups
- reflected light from the splash guard. Did you use lenses?
- possible the reaction with the vapors from the skimmer to speed up the process.
- did you use a solvent to clean the area prior to adding the LED? If Yes, add this as a contributor, even if the discolouration did not show up in your first day. I have used Ethanol before on anodized parts and the end result was similar to yours (dicolouration).

I exclude the stray currents and/or any type of galvanic corrosion. You did not use screws to attach the LDS's, right?

 

[AdamS]

I have these same heat sinks, and I recall thinking the annodization looked a little crappy, but the price is right.  I am not home now but will have a look at mine when I am home in a week.

I know Salty Cracker has these same heat sinks, maybe he can have a look and see if he has this going on at all.

 

[Pistol]

It looks like a piece of wood, pine maybe, that rapidled painted to look like a heatsink, LOL!
But seriously, I would contribute it to poor quality anodizing, aesthetic only.

 

[MrHermit85]

I have the same thing on my heatsink. It happened under my UV that burned up so I would definitely assume it's because of heat. My heatsinks are also from rapidled and I have also noticed similar discolouration in other areas under my LEDs. There are perfect rings under every LED intact. Mine are further apart than yours which is probably why yours is so severe.

So no worries I guess, it's not as if you have to look at that side of the heatsink

 

[MrHermit85]

It's odd that your one discoloured a different colour though... Perhaps the heatsink were from different batches or suppliers?

 

[Victoss]

It's odd that your one discoloured a different colour though... Perhaps the heatsink were from different batches or suppliers?

I think one is just further along then the other for what ever reason.

Ascetically you don't even notice it on the outside of the heatsinks and they will be put in a hood in the very near future anyways.

No optics on the leds and was even considering putting some on while I have the unit off but it will only be 6" or so off the water so seems like there not needed. And I don't remember if I used something to clean the heatsink when I put the first set of LEDs on but last night I just upgraded it and used some alcohol wipes for electronics on the heatsinks, it's probably what I did a year ago.

 

[MrHermit85]

[quote author=MrHermit85 link=topic=7496.msg77281#msg77281 date=1390057404]
It's odd that your one discoloured a different colour though... Perhaps the heatsink were from different batches or suppliers?

I think one is just further along then the other for what ever reason.

Ascetically you don't even notice it on the outside of the heatsinks and they will be put in a hood in the very near future anyways.

No optics on the leds and was even considering putting some on while I have the unit off but it will only be 6" or so off the water so seems like there not needed. And I don't remember if I used something to clean the heatsink when I put the first set of LEDs on but last night I just upgraded it and used some alcohol wipes for electronics on the heatsinks, it's probably what I did a year ago.
[/quote]

 

[MrHermit85]

[quote author=MrHermit85 link=topic=7496.msg77281#msg77281 date=1390057404]
It's odd that your one discoloured a different colour though... Perhaps the heatsink were from different batches or suppliers?

I think one is just further along then the other for what ever reason.

Ascetically you don't even notice it on the outside of the heatsinks and they will be put in a hood in the very near future anyways.

No optics on the leds and was even considering putting some on while I have the unit off but it will only be 6" or so off the water so seems like there not needed. And I don't remember if I used something to clean the heatsink when I put the first set of LEDs on but last night I just upgraded it and used some alcohol wipes for electronics on the heatsinks, it's probably what I did a year ago.
[/quote]

When I upgraded mine I didn't even clean the heatsinks lol

 

[Victoss]

[quote author=Victoss link=topic=7496.msg77304#msg77304 date=1390066918]
[quote author=MrHermit85 link=topic=7496.msg77281#msg77281 date=1390057404]
It's odd that your one discoloured a different colour though... Perhaps the heatsink were from different batches or suppliers?

I think one is just further along then the other for what ever reason.

Ascetically you don't even notice it on the outside of the heatsinks and they will be put in a hood in the very near future anyways.

No optics on the leds and was even considering putting some on while I have the unit off but it will only be 6" or so off the water so seems like there not needed. And I don't remember if I used something to clean the heatsink when I put the first set of LEDs on but last night I just upgraded it and used some alcohol wipes for electronics on the heatsinks, it's probably what I did a year ago.
[/quote]

When I upgraded mine I didn't even clean the heatsinks lol
[/quote]

I just thought with all the salt spray around the tank and dust on the heatsinks I should wipe the area I'm thermal gluing to.

 

[MrHermit85]

It's an excellent idea! I just got lazy. Plus there was no salt spray on my fixtures.