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A Guide to Pulley Coatings and Applications

a guide to pulley coatings and applications

Timing belt pulleys are one of the most common equipment pieces utilized in hundreds of applications spanning from automobiles to treadmills and sewing machines. Dozens of everyday and advanced technologies require synchronous timing belt drive systems.

However, in certain applications, a standard timing belt pulley is insufficient to withstand unique or harsh environmental conditions. In such cases, pulley coatings are implemented. Regardless of pulley material, a variety of available coatings assist in protecting the system from failure in unique circumstances.

What are Timing Belt Pulleys?

Timing belt pulleys are specialized systems designed to engage a pulley belt without the possibility of timing or averting misalignment. These pulley products are ideal for synchronous applications. Other pulley options, such as multi-ribbed or variable speed systems, do not provide the consistency required for the homogenous rotation of two shafts.

Steel Pulley Coatings

A variety of coatings are available for steel pulleys. Although steel pulley stock is already designed to withstand hot or cold environmental conditions, additional coatings are often necessary for certain circumstances.

Black Oxide Coating

Black oxide coating is a black oiled finish used to protect steel from rusting. The black oxide coating process is created by a chemical reaction that forms an integral protective surface. To provide additional corrosion protection after the conversion coating process, a wax or oil is often applied.

The black oxide coating process is utilized in a plethora of industrial applications, on a wide variety of metals – including steel.

The benefits of black oxide include:

  • The ability to provide aesthetic appeal without affecting dimensional stability
  • Inexpensive coating option
  • Versatility for a diversity of metals
  • Durability – the only way to remove the coating once applied is via mechanical or chemical means
  • Protection of the treated service against corrosion

Clear Bright Zinc

Zinc chromate is a shiny silver finish (with slight blue tint) used to protect steel from rusting. Although the shiny appearance is aesthetically pleasing, nickel or chrome finishes are often preferred for purely cosmetic applications.

Zinc chromate offers an additional layer of protection against corrosion over the zinc layer.

The benefits of clear bright zinc plating include:

  • Excellent protection of the treated service from corrosion
  • Cost-effective
  • Widely available
  • Clear bright zinc is an economic solution

Electroless Nickel

Electroless nickel protects steel from rust and abrasion. Electroless nickel coating is a chemical process that deposits a nickel-phosphorus alloy on a material surface. Unlike an electrolytic coating, electroless nickel is formed without an external electrical current. In fact, the process is simple – a material is dipped into a water solution that contains nickel salt and an applicable reducing agent.

The benefits of electroless nickel include:

  • Abrasion protection, as nickel is extremely hard
  • Good corrosion resistance
  • Improved lubricity

Aluminum Pulley Coatings

Multiple coating options are available for aluminum timing pulleys. Once more, although aluminum pulley stock is a strong, light material, excellent for a variety of applications, coatings serve to enhance the longevity of the material.

Clear Anodize

This aluminum pulley coating helps prevent surface pitting and corrosion. The anodizing process involves chemical preparation. An electric charge is then applied to the material, resulting in a thick, anodic oxide layer that is stiffer and more resistant to corrosion.

The benefits of a clear anodize coating include:

  • Minimal cost
  • Coatings can be colored with a variety of dyes
  • Anodization increases aluminum stability
  • The bright coating increases aesthetic appeal
  • Increased temperature control

Hard Anodize

This aluminum pulley coating is used to prevent surface pitting, corrosion, and parts wear. Like clear anodizing, hard coating anodizing is an electrochemical process that improves corrosion-resistance and durability in aluminum.

The difference between clear anodizing and hard anodizing lies in the results. Hard anodizing provides increased wear resistance and a smoother finish.

In the hard coating anodizing process, an aluminum oxide layer enters the surface of the aluminum. The material is then placed in a sulfuric acid bath for a designated period of time. The thickness of the coating is determined by time spent submerged in the acid bath.

The benefits of a hard anodize coating include:

  • Coatings can be colored with a variety of dyes
  • Resistant to peeling or chipping
  • Easy to clean and maintain
  • Increased lubrication
  • Improved abrasion resistance
  • Flame resistance

Electroless Nickel

As previously explored, electroless nickel is a high-quality coating that protects aluminum from pitting, corrosion, and parts wear. Although slightly more expensive, electroless nickel is an excellent coating for steel and aluminum pulleys.

In the process of coating aluminum, the metal must be cleaned of oil, grease, etc. and stripped of metal oxides present on the surface. After, a process occurs with deposits a thin zinc immersion on the surface of the metal. An electroless nickel strike finally removes immersion zinc to reveal the aluminum surface.

Similar to the coating for steel pulleys, the benefits of electroless nickel include:

  • Abrasion protection, as nickel is extremely hard
  • Good corrosion resistance
  • Improved lubricity

Illinois Pulley & Gear

At Illinois Pulley & Gear, we are dedicated to providing the highest-quality timing steel pulley products to meet a variety of industry needs. Our solutions are completely customizable upon order – thus, manufacturers can request their precise equipment from us without adapting it elsewhere.

Our made-to-order timing pulleys may be produced with other customer specified requirements such as: pitch, number of teeth, bore size (English or Metric), keyway, setscrews, lightening holes, and timing marks. To get in touch with our team about a customized solution for your needs, reach out at 847.407.9595 or via our online contact form!