A Guide to Coated Wire Rope

Wire ropes are key components for both functional and aesthetic applications in a wide variety of industries. In both cases, coatings can improve the performance and longevity of the coated wire rope.

This article will cover the basics of coated wire rope, including its purposes, applications, benefits, and key features.

Coated wire rope has several benefits over an identical uncoated wire rope:

• The coatings protect the wire rope from exposure to oxygen, water, salt, or other harsh chemicals.
• Coatings act as a shield against scratches, dirt, and water.
• Coatings extend the life of a cable. The resistance to corrosion and damage offered by coatings makes the wire rope last a lot longer than an unprotected rope.
• Coating colors provide visibility and enhance aesthetics.

There are many kinds of coatings, but this article is concerned with the key types that are the most commonly used:

• PVC (Poly-Vinyl Chloride) Coated Wire Rope & Aircraft Cable
• Nylon Coated Wire Rope & Aircraft Cable
• HDPE (High-Density Polyethylene) Coated Wire Rope & Aircraft Cable
• Black Finish (Powder Coated or Anodized) Coated Wire Rope & Aircraft Cable
• Plastic (Polypropylene) Impregnated Wire Rope

PVC, Nylon, and HDPE coatings are known as “cable sheaths” because they are extruded plastic jackets that enclose the coated wire rope in a plastic jacket.

To create these cable sheaths, a technician feeds plastic resin pellets into the hopper of the extruding machine that passes the cable, which can be bare stainless steel or galvanized, through a layer of molten plastic. The plastic jacket forms the final outer diameter as it flows through dies.

The extruder is precisely calibrated to feed the wire rope at a specific speed and temperature. The difference between the inner cable diameter and the outer diameter of the coated cable represents the coating thickness.

Determining Coated Wire Rope Strength

Coatings have no impact on the strength of the internal cable, notwithstanding termination considerations. The strength of the coated wire rope is determined entirely by the material, construction, and diameter of the internal cable.

It’s strongly suggested that the plastic coating be stripped before swaging end fittings for load bearing applications. For example, if the wire rope is 3/16” coated to 1/4″OD, then a 3/16” end fitting is suggested for swage installation at the stripped end.

Coated Wire Rope Assemblies & Strength Considerations

When discussing coatings, people often wonder if the coating needs to be stripped at the terminations. To answer this, you must also consider the application and the working load.

For security cables, the loops can be swaged over the coating. For lock up, like in retail security, the loop is meant to be a theft deterrent, so the full pull capacity of the wire rope is not necessary to accomplish that purpose.

For some very light-duty lanyards with loop ends that have working loads of approximately 5 to 25 lbs., stripping the loops may not be necessary. For some moderate-duty lanyards with loop ends that have working load limits of approximately 50 to 100 lbs., it may be appropriate to semi-strip the loop. To semi-strip the loop, only the second segment that turns back into the sleeves is stripped.

For example, with 1/8″ coated to 3/16”OD, if the 1/8″ crimp sleeve is 5/8″ long uncrimped, and becomes 3/4″ long crimped, then one would use a 3/4″ strip length. This results in the visible portion of the loop being coated, but since the second segment is stripped, it increases the coated loop strength relative to a fully coated loop. A pull-test should be performed to verify results of coated loops and semi-stripped coated loops.

Lifting and Towing Applications

Types of Coatings for Wire Rope and Aircraft Cable

Lifting and Towing Applications

PVC, also referred to as Vinyl, is the most common type of coating for coated wire ropes and aircraft cables. PVC is economical, general purpose, and often comes in a variety of colors.

One advantage of PVC is that it can be dyed to match a variety of colors, including primary colors such as red and blue, or specific color variants such as olive and forest green. It has a low-friction surface, making it abrasion-resistant. PVC is also resistant to damage from continuous UV exposure and is completely waterproof.

PVC is the best choice of coating coiled cables, such as with lanyards and trailer safety cables, due to its flexibility.

Nylon Coated Wire Rope

Nylon is the second most common form of wire rope coating. Nylon is more abrasion-resistant than PVC. Since Nylon is harder than PVC, it has better resistance to impact. Nylon’s strength makes it good for applications with friction and constant tension. Nylon’s abrasion-resistance, combined with its flexibility, gives it the ability to cycle without tearing.

Nylon is most used in lifting and rigging applications in military and aerospace environments (MIL-DTL-83420 Type II), push-pull controls, gym equipment, and a variety of conveyor systems.

HDPE Coating

High-Density Polyethylene, or HDPE, is a less common coating used in select applications where its features are most desired, including underground burial structures.

Black Finish (Powder Coated or Anodized)

Unlike the previous plastic coatings, black finish cable is created by applying a powder substance to the wire rope.

Powder coatings do not offer the same damage and weather resilience as plastic coatings, but they still preserve the metal beneath. This type of coating also has a matte finish, which is desirable in entertainment applications like theater, concert stage, and film productions because it reduces the reflective sheen of wire ropes and cables. Other applications where the black matte finish comes in handy includes trade show rigging and bow hunting.

Plastic (Polypropylene) Impregnated Space Lay Cable

Plastic-impregnated cable is a higher-cost, specialized coating for use in particularly harsh environments where the possibility of condensation or internal abrasion is intolerable.

The SPACE-LAY design starts with galvanized wire ropes. Each strand of the rope is spaced apart from each other and the cable core. The spacing allows the extruded polypropylene plastic to encapsulate each strand. The inner-wire strands do not rub against one another, and the plastic coating cannot be peeled away, making the coated wire rope much more resistant to internal and external damage.

This type of coating is most common in heavy industry, naval and marine environments, oil and gas extraction, mining, and logging.

Learn More About Coatings

Coated wire ropes offer significantly improved longevity and resilience compared to uncoated wire ropes. Lexco Cable offers all coatings discussed in this article, either in-house or through a network of trusted associates, for a wide variety of cable designs. Find out more about coated wire ropes and how Lexco Cable can help you, and get a quote today.