Tin-Coated Copper Wire Vs. All-Copper Wire

Inhibition of wire corrosion Ah, the great debate over which type of wire is best for landscape lighting. In this blog, we will put an end to this back-and-forth by sharing four major benefits of tin-coated wire—specifically CAST’s No-Ox marine-grade tin-coated copper wire. First, there’s no question that corrosive effects of the outdoor environment present unique challenges to landscape lighting. Every component of the lighting system is subject to moisture, heat, cold, and physical abuse. Landscape lighting wire is especially critical since its corrosion leads to degradation of lamp performance and eventually complete system failure. In this blog, we will address the three primary factors that determine long-term integrity of  a landscape lighting system:

  1. Inhibition of wire corrosion
  2. Preservation of wire conductivity
  3. Optimization of wire solderability

5 Reasons Why CAST’s No-Ox Tin-Coated Copper Wire is Tops

1. Marine-grade protection against wicking

Wicking is the migration of water and electrolytes under wire insulation. This moisture travels from wherever the wire has been cut including splice points, socket connections, and transformer terminals. Wicking causes a progressive oxidative corrosion of the wire. The wicking problem has long been recognized by marine engineers since moisture is constantly present in the marine environment. These engineers, working in concert with regulatory and advisory agencies, developed marine-grade standards for boat wiring. These standards require tin-coated copper wire. The presence of moisture in the landscape makes outdoor lighting wiring more akin to marine applications (think irrigation systems or oceanfront homes) than to wiring used in the low-moisture indoor environment. For this reason, CAST has adopted the marine-grade standard by introducing No-Ox tin-coated wire.

2. Oxidative corrosion prevention & conductivity protection

Electrical conductivity is a measure of a material’s ability to carry an electrical current. Copper is an excellent conductor, making it ideal in all electrical applications. However, in the presence of air and moisture, its surface oxidizes forming a layer of copper oxides that conduct electricity very poorly. This layer is not initially a problem since the layer is very thin and actually serves to protect the underlying copper. In an outdoor corrosive environment, however, the oxide layer progressively extends deeper into the copper strand and eventually oxidizes the entire thickness. This decrease in conductivity severely compromises the lighting system. Landscape lighting wire is especially prone to this severe corrosion because it is a stranded wire with very thin strands. Lighting installers often see the devastation of this effect when they pull old wire from the ground and see the strands completely blackened and brittle. Tin-coating the wire protects from this type of progressive corrosion and loss of conductivity in two ways:

  1. Tin oxidizes before copper

The tin coating differs in electrical potential from copper in a way that causes the tin to be oxidized in preference to the copper. In other words, instead of a progressive deepening of the corrosion into the strand, the tin must completely oxidize before the copper interior is subject to corrosion.

  1. Greater conductivity of tin oxides

While copper oxides are very poor electrical conductors, tin oxides maintain good conductivity. This benefits the long-term conductivity of the entire wire bundle. Note: the initial conductivity of the tin coating is lower than copper, leading to a slightly higher voltage loss at time of installation. This difference is offset over time since the tin coating largely maintains its conductivity while the oxidized copper conductivity significantly increases over time.

3. Tin-coated copper wire is required

In addition to the marine-grade applications, tin-coated copper wire is required (various UL listings) for the internal wiring of any appliance subject to heat and humidity. CAST also uses tin-coated No-Ox wire for all internal wiring of its fixtures and transformers.

4. Reputation & homeowner perception

CAST’s No-Ox tin-coated copper wire is considered the highest quality wire available. Lighting designers who maintain an uncompromising attitude toward quality will earn the best reputations and get the best jobs. Additionally, homeowners readily see the value in using marine-grade wire. If you, the professional, assure them that the use of this wire will add longevity and reliability to their lighting system, they will be even more willing to absorb the extra cost. (Keep in mind that No-Ox wire is just a few dollars more than all-copper wire.)

5. Solderability

Landscape lighting installers use a variety of methods for making wire connections in the field. Of these methods, soldering provides the most secure, corrosion-resistant splice points. In fact, CAST teaches this soldering method at all its seminars and workshops. Since tin solder is the preferred type, it stands to reason that tin-coated wire is the best recipient of this solder. The resultant connection provides a seamless surface of tin that extends from the solder point along the entire length of the wire. This is critical for corrosion prevention since corrosion occurs most aggressively when two dissimilar metals are in contact with each other and exposed to the environment. A tin solder connection on an all-copper wire is an invitation for corrosion to occur at the copper-tin boundary. Soldering can be especially problematic when old wire is soldered. This situation occurs frequently since installers are often called upon to add fixtures to an existing system. Tin-coated wire maintains good solderabilty as it oxidizes over time. Copper oxides, on the other hand, are extremely resistant to solder. An installer trying to add new fixtures to a system with all-copper wire, may be forced to replace entire wire runs while a system with tin-coated wire may be cut and re-soldered to make the new connections.

The Choice is Easy

As you can see, there are many benefits of using tin-coated copper wire for landscape lighting, and even more so when choosing CAST No-Ox wire. Preventing wire corrosion, preserving wire conductivity, and optimizing wire solderability are three primary reasons to opt for tin-coated copper wire, which unquestionably influences its reputation and homeowner perception of this superior quality product.