LED fixtures and avoiding corrosion

[hobbzz]

I recently read three pages of led "fixture" builds and the one thing that's missing from most of them is the actual fixture lol. Most people just seem to have non-anodized aluminum framework with the led's and wiring mounted to it hanging bare, just inches over rapidly evaporating highly corrosive salt water...

What is everyone doing to prevent corrosion and rust? You would think exposed metal frame work and exposed wiring is gauranteed to rust. I'm thinking of building a fixture out of acrylic (with fans of course), but if a simple acrylic shield between the framework and the water is proving to be enough I'm all for the easier route.

 

[der_wille_zur_macht]

There are a few specific things you might want to consider protecting against. Corrosion, from moist air, and actual splashing water. You also need to consider the performance or maintenance impacts of any specific solution you want to apply.

Corrosion is not a problem is the fisture is designed and built correctly. Wiring should all be tinned, which protects the bare copper even up inside the insulation. Hardware, i.e. screws, bolts, nuts, and so on, can be chosen in stainless to eliminate corrosion. Other than that, the types of metal that are exposed are generally very resistant to corrosion and require no additional protection IME. Contacts on mcpcbs are generally either gold, or are tinned. Tin/lead or silver solder are all highly corrosion resistant if proper flux and cleaning procedures are followed. That leaves the bare aluminim heatsink, which anecdotally tends to resist corrosion better than you might expect.

To protect from splashes, which can contribute to not only corrosion but also physical damage from thermal shock, a splash shield is typical unless the fixture is two feet or more above the water.

Generally, these practices are more than adequate. I have fixtures that are several years old and look brand new, and I know many others who do as well.

 

[hobbzz]

Good to hear. Easier sounds much better lol. I was surprised at the lack of discussion on the subject. Thanks for the help!

 

[kcress]

You can also use tight optics and mount your fixture against the ceiling which precludes any other splash protection being needed.

 

[Devaji108]

yes good question. and great answers.
PS love your avatar!!

 

[fingas]

Hardware, i.e. screws, bolts, nuts, and so on, can be chosen in stainless to eliminate corrosion.

One word of caution here is that where stainless and aluminum (certain alloys) come in contact in the presence of saltwater you can have galvanic corrosion. Not a huge problem usually but it can be.

That leaves the bare aluminim heatsink, which anecdotally tends to resist corrosion better than you might expect.

We use bare aluminum conduit and fittings around cooling towers alot and the aluminum holds up really well except where stainless clamps are used against the aluminum.

 

[der_wille_zur_macht]

Indeed i suppose that is possible whatever alloys the heatsinks and screws I use must be compatible, as I have never seen a hint of it on any of my fixtures. These days I use thermal compound instead of screwing LEDs down so there's vastly less hardware involved anyways.

 

[ReefEnabler]

I ran my LEDs about 12" from the water for over a year and there were no corrosion issues... and I took 0 measures to protect the fixture or LEDs aside from optics.

however there was one BIG issue.... my stupid elbows kept breaking the optics off when I was cleaning the tank :lol: next time I will definitely either put them further away or build an enclosure just so I don't mess it up by hand.