Can someone explain what is causing this white scale to appear on the copper pins and on the block of this LED light connection? The seal at the connection is supposed to be watertight. On occasion, there is a white (crystallization) that forms at the PC board, pin and on the block at this connection. These lights are exposed to sun and rain and are located 5 miles from coastal waters. There is power and data flowing through these connects and both get affected causing the lights to go out.!(https://i.stack.imgur.com/6tFew.jpg)
Copper is a material that corrodes, just like any other. When copper corrodes, it will turn into copper carbonate (Cu2CO3(OH)2), but near the sea it might become copper chloride (Cu2(OH)3Cl) as well. When water is involved, like in your case, there may be an effect called efflorescence. Efflorescence "is the migration of a salt to the surface of a porous material, where it forms a coating". This usually forms in a crystal form, since it's formed of salt. This is what creates the white buildup sometimes found on water pipes for example:
So basically, you're getting water infiltration. The easiest solution to solve this is using dielectric grease. Or get a better seal for your electronics.
I agree with the theory of water ingress. On top of that I would like to add following.
IP65 has a complete protection against water jets and is dust proof. The protection level itself forms a part of the problem due to the following.
A lower temperature of the enclosure in relation to the surrounding air causes a difference in pressure with an inflow of outside air as result. If the temperature becomes low enough the moisture in the air starts to condense. Compare this with dew in the morning. Now the trouble starts.
Water can't escape. Only when the inside enclosure temperature becomes high enough to evaporate the water or prevent condensation in the first place and the inside presure becomes higher than the outside pressure the vapour is forced out and corrosion is prevented.
Any encloser with enough heat production or forced dry air is able to fulfill these conditions. The connector presented by OP does not fulfill these conditions and corrosion can not be prevented.
The only way out is to use enclosures that can ventilate to the outside and yet are protected against splash or sprayed water. For this the IP standard does not yet offer any help.
You can try to clean but the problem remains.