Why Are Coatings Important for Agricultural Fasteners?

Why Are Coatings Important for Agricultural Fasteners?

Equipment used in the agriculture industry must withstand heavy use and continuous exposure to the elements, fertilizers, and pesticides. In addition to large equipment components like tiller blades, wheel assemblies, tractor panels, and motorized components, large quantities of properly selected metal fasteners are needed to hold parts and assemblies together securely. Those fasteners must be strong enough to bear static and dynamic loading as well as environmental conditions that contribute to corrosion.

When fasteners become corroded, they lose structural strength and holding power, putting equipment and operators at risk. Here, we will look at the dangers associated with fastener corrosion and some of the options for protection. We’ll also explain salt spray testing and different types of protective zinc coatings for fasteners.

Dangers of Corrosion

Corrosion takes many forms, including uniform corrosion that forms on the surface of a substrate due to moisture, galvanic corrosion between dissimilar metals that react when exposed to electrolytes, localized pitting, stress and fatigue corrosion, and others. Regardless of the type, corrosion spreads quickly and causes metal fasteners to degrade and weaken.

When fasteners like nuts, bolts, screws, washers, rivets, nails, or retaining pins become corroded, the parts and equipment they hold together can break or fall apart. This is dangerous for operators and any living things nearby. It also risks damage to blades, panels, tires, and other components. Because fasteners play such a critical role in the performance of agricultural equipment, they must be incredibly resistant to corrosion.

Corrosion risk factors include:

• Harsh chemicals like liquid nitrogen in fertilizers
• Constant exposure to weather including rain, ice, snow, and UV radiation
• Constant wear from heavy use during planting and harvesting seasons
• Moisture, dirt, and debris from constant work in fields, especially in areas with acidic soils

Protecting Against Corrosion With Fastener Coatings

Specialized coated fasteners benefit from long-lasting protection against corrosion in many agricultural and farming applications. The coatings create a physical barrier between sources of corrosion and the underlying metal surface.

Depending on the operating conditions, there are many coating options available for agricultural fasteners, including:

• Powder coating: Applying protective powder on metal components and baking it on for a highly durable finish
• Metal coatings: Coating components with protective metals such as cadmium, phosphate, zinc, or zinc flake by brushing, dipping, or other methods
• Electroplating: Submersing components and a piece of protective metal in an electrolyte solution and introducing electrical current, which forms a permanent layer of protective metal on the components; often used to create chrome, nickel, zinc, or zinc flake layers

Salt Spray Testing for Corrosion Resistance

Coated fasteners are characterized by their dimensions, material, and intended end use. They are also rated for their predicted resistance to corrosion. One of the most common tests is salt fog testing, or salt spray testing. In this test, sample fasteners are placed into a closed testing chamber and sprayed with high-pressure salt water for an extended period of time. The conditions are designed to replicate real-world exposure to salinated water or sea spray on the fasteners.

The amount of time that passes before the metal begins to corrode or break down is measured, and the protective coating is rated to resist corrosion for that amount of time. Depending on the material being tested, ratings can range from 24 to 1,000 hours or more.

Zinc Coatings for Chemical and Corrosion Resistance

While there are numerous coating materials and methods, zinc and zinc flake are among the most effective and durable.

Zinc can be applied to a substrate by dipping the piece in molten zinc, then spinning off the excess to produce a thick, strong protective layer. It can also be electroplated, which creates a very even but somewhat thinner layer.

Another option is zinc flake, which is a mixture of zinc and aluminum. Zinc flake coating is done in two applications: a base coat and a topcoat, each baked onto the substrate to form a solid layer. Zinc flake coatings can resist salt spray for up to 1,000 hours. This makes it an excellent choice for agricultural fastener applications which must tolerate fertilizers, moisture, pesticides, and other hazards.

Contact Associated Fastening Products for Agricultural Coated Fasteners

When selecting fasteners for agricultural equipment and machinery, it’s important to select metals that are compatible with other equipment components. However, it’s also critical to choose a protective finish for those fasteners to delay or prevent corrosion. Strong fasteners keep equipment and operators safe, and extend the useful life of machinery.

Contact Associated Fastening Products to learn about the types of fasteners we supply for the agricultural industry or request a quote for specific pricing details.