What are the Different Types of Finishes for Palnuts?

Huyett Marketing Department
05/27/2021

At Huyett, we stock a diverse selection of fasteners so our customers can quickly find the part they need for any project. Of course, that applies to the thousands of sizes, shapes, and fastener types in our catalog. But it also applies to the many finish options, each of which affects fastener appearance and their suitability for use in different environments.

This article explores the qualities of the most popular Palnut fastener finishes and how they are achieved.

What is a Palnut?

Palnuts are a type of engineered fastener, which are alternatives to traditional fasteners such as screws, nuts, and bolts. They include push‑on fasteners, self‑threading nuts, lock‑nuts, On‑Sert® fasteners, and more. You can learn about Palnuts and other engineered fasteners from
Huyett’s Guide to Engineered Fasteners, including panel and trim clips, wire management clips, and self‑locking threaded nuts.

Types and Properties of Palnut Finishes

We stock Palnut fasteners in many different finishes, including combinations of finishes. Each has unique properties, so let’s take a closer look at the most popular Palnut finishes ordered from our catalog.

Stainless Steel

While stainless steel is a material, not a finish, many customers choose stainless steel Palnut fasteners because they are inherently corrosion resistant. We stock Palnut Push‑On fasteners in both 301 stainless steel and 302 stainless steel. As with all steels in the 300 series, 301 and 302 are austenitic stainless steels with excellent corrosion resistance, strength, and ductility. 302 stainless steel includes more chromium and nickel, increasing its corrosion resistance. 302 stainless steel is often used in scenarios where corrosion and contamination resistance are a priority.

Degreased

When selecting stainless steel Palnuts fasteners, customers may also choose to have them degreased to remove oils, greases, and other contaminants. Degreased components are often used in aerospace, food, and medical applications where contamination avoidance is a priority.

Stainless Steel

Zinc Finishes: Hot Dip Galvanized, Electroplated, and Mechanical

Galvanization coats a steel part in a zinc finish. The zinc coating alloys with the underlying metal and the external surface reacts with the atmosphere to form zinc carbonate, which resists corrosion better than the underlying steel.
Once a component is galvanized, it has a silver or dull grey appearance, but galvanized parts can be painted or layered with other finishes.

There are three common galvanization processes. All aim to cover a part in zinc, but the thickness and quality of the zinc layer differ according to the process.

Zinc hot‑dip galvanization
dips the component in a bath of molten zinc after degreasing and pickling.

Zinc mechanical galvanization
is carried out at room temperature. The parts are placed in a rotating barrel with zinc powder, glass beads, and various chemicals. Energy from the moving beads causes the zinc particles to mechanically weld to the steel’s surface.

Zinc electroplating
is an electro‑deposition process. The fasteners are submerged in a bath comprising dissolved zinc and other chemicals. When an electrical current is applied, a thin layer of zinc is deposited. The thickness of the layer varies according to time and current. Zinc electroplating improves the corrosion resistance of fasteners, including engineered fasteners, screws, nuts, and many more. We stock Palnut fasteners with a range of zinc electroplating thicknesses, with or without additional finishing steps.

Galvanization is less expensive than stainless steel. It provides a moderately corrosion‑resistant finish with excellent electrical conductivity. However, galvanized finishes are not suitable for environments with frequent acid exposure. They should also be avoided when fasteners are in contact with copper or brass, especially in moist environments.

Yellow Chromate

Yellow chromate is a form of zinc chromate — a yellow powder used in chromate conversion coating. Conversion coating causes a thin layer of the compound to adhere to the fastener’s surface, increasing corrosion resistance and durability. Yellow chromate is often used with aluminum, zinc, and other metals. Yellow chromate finishes cannot be applied directly to steel components; however, they can be applied to steel fasteners with a phosphate coating and to zinc‑plated or galvanized fasteners. Yellow chromate is an excellent paint primer.

Trivalent Finish

Trivalent finishes use chromium electroplating to provide a hard corrosion‑resistant coating. The name “trivalent” derives from the chromium compound used in the electroplating process. Historically, chrome plating used chromium trioxide, a hexavalent chromium compound. Hexavalent chromium is highly toxic, and modern chrome plating uses safer trivalent forms of chromium sulfate or chromium chloride instead.

It should be noted that chrome electroplating is not the same as the chromate conversion process used for yellow chromate finishes. Chrome plating is an additive coating, whereas chromate conversion, as the name suggests, converts part of the underlying metal’s surface into a protective layer.

Phosphate Finish

Phosphate finishes use a phosphate conversion coating process to apply a thin layer of iron phosphates to steel parts. Phosphate conversion coating improves the corrosion‑resistant qualities of steel fasteners. When used with steel, phosphate finishes are usually painted or impregnated with oil.

We stock a variety of phosphate‑finished parts, and our customers can choose from phosphate, phosphate with black paint, phosphate with two coats of paint, and phosphate and oil combination finishes.

GEOMET

GEOMET® is a water‑based zinc flake coating for corrosion resistance. It is primarily used as an environmentally friendly alternative to galvanization. It has the added benefit of protecting metals from hydrogen embrittlement.

Multi-Layered Palnut Finishes

We have listed the seven most popular finishes for Palnut fastener finishes stocked by Huyett. However, we also stock fasteners with other finishes, including black oxide, copper mechanical, Dacromet, and zinc‑aluminum.

Many of the finishes we have explored are available in combination with others — for example, phosphate with oil and zinc with trivalent finishes and sealer. We aim to provide the greatest possible diversity of finishes so that our customers can select the perfect component and finishes for their projects.

Want To Learn More?

To learn more about Palnut Push‑On Fasteners and other engineered fasteners, read
Huyett Guide to Engineered Fasteners or
contact a sales team member.