The number one issue confronting boaters when installing and maintaining exterior lighting is the effect the marine environment has on metal and electrical devices. Every boater knows the problems salt water can create, and metals and electrical components not well designed or properly protected can be destroyed in short order once exposed to corrosive salt water. Compounding the problem is the tendency for humidity levels to reach very high levels in the areas in and around marine environments, and when combined with high levels of salts in these same areas, they can really wreak havoc on equipment. For these reasons, it is critical to the longevity and reliability of exterior boat light to ensure the use of equipment capable of withstanding the effects associated with marine use LED lighting.
The biggest problem for electrical devices onboard a boat is the constant exposure to salt water. Most metals are subject to the effects of corrosion in one form or another however, in the presence of an electrolyte, this process can become greatly accelerated. As you already know or have probably deduced, salt water is unfortunately a very good electrolyte. The corrosive process at work here is called galvanic corrosion, and it occurs when two dissimilar metals are joined together in the presence of an electrolyte. If we join two metals, such as a zinc bolt and a stainless fitting and expose them to sea water, we would see the zinc bolt rapidly oxidize until it eventually loses its structural integrity and fails. This process is constantly at work onboard a boat, and as a result boaters find themselves always faced with paying close attention to the metal structures onboard and keeping them well maintained and protected.
The issue of corrosion is even worse for electrical devices. This is in large part because of the electrical current that is constantly passing through them as they operate, which can serve to even further accelerate the process of galvanic corrosion. When we consider that the internal electronics of a device contain a wide variety of metals in their construction including zinc, steel, lead, tin, aluminum, and other metals, the issue of corrosion becomes critical indeed. If you need any proof of this, simply take a basic transistor radio onboard once and allow it to become exposed to some light salt water spray. The radio may continue to function for a day or so, but it is almost guaranteed that within two days corrosion will have attacked the internal components to the point of causing failure.
So what is the issue for the standard exterior boat light fixture? Probably the biggest issue with standard incandescent and HID boat lights used for exterior illumination whether they are spreader fixtures or simple navigation lights is the corrosion of the internal bulb sockets and wiring/contacts. Just about any boater who has serviced a standard spreader light has come across the all too common bulb permanently welded to its socket by corrosion. If the housing seal is less than perfect, or fails, it is almost certain that salt spray and high salt content humidity will contaminate the interior quickly begin the process of galvanic corrosion. Once this starts, it is difficult to control or stop, even if caught in the early stages, and most boaters don’t even realize it is occurring until the light fixture has failed altogether. Mounting hardware itself is constantly exposed to sea water and humidity, and unless it is composed of the most resistant metals, will also fail in short order.
A big part of the problem here is the difficulty in effectively sealing the housing on an incandescent or HID boat light. Although high quality gaskets and good tolerances between housing and sealing lenses and doors can effectively lock out moisture in all its forms, the constant exposure to UV light, heat, humidity, and stresses from a boat that’s underway will cause them to eventually fail. There is little remedy for this aside from a diligent routine of inspection, maintenance and replacement, and this can become difficult and time consuming to execute consistently. With all of the work that goes into maintaining a boat in seaworthy condition, it is just all too easy to overlook light fixtures until it is too late and corrosion has taken its toll.
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