An electropolished automotive spring (front) sits next to a raw part. Electropolishing removes microscopic defects in parts that undergo extreme forces, extending product life.

Microdefects on the surfaces of stamped and formed parts can compromise the strength and corrosion-resistance of springs and flexible auto parts such as hose clamps and clips. These weaknesses introduced during manufacturing can lead to premature part failure.

Springs and other automotive parts that must flex and torque undergo tremendous stresses during stamping or forming, creating defects that must be addressed before final use. Even the smallest imperfection creates a weak point in the part that, if not treated, can grow with use as the part flexes and bends – a phenomenon known as the notch effect. Placing stress on notch defects can cause part failure.

Electropolishing

Automakers typically use electropolishing to produce a bright, shiny, smooth finish on metals. Manufacturers immerse a part in an electrolyte bath that includes a flowing current. The process removes a very thin layer on the surface of the part, usually 0.0005" to 0.0010" from the thickness or diameter. Removing the outer skin of metal also removes embedded debris, contaminants, burrs, minor scratches, and other imperfections such as minute cracks.

Parts makers can determine the thickness of the layer to be removed using processing samples followed by die-penetrant testing, scanning electron microscope (SEM) analysis, or fatigue-life testing. Thickness is carefully controlled and can be replicated repeatedly to produce consistent results.

With electropolishing, each part is fully immersed in the electrolyte bath, an advantage for parts with multiple cutouts, surfaces, or edges, such as hose clamps. Immersion guarantees that the entire part will be treated, resulting in a uniformly smooth finish. It is effective on various materials, including stainless steel.

Reducing corrosion risk

While the notch effect is the greatest cause of premature performance failure in automotive springs and other movable parts, corrosion also weakens parts and reduces longevity.

Corrosion results from chemical reactions between a metal and the surrounding environment. Irregularities in the metal surface can be initiation sites for corrosion. Pitting and crevices can develop, weakening the part and potentially causing premature failure.

A smooth, electropolished surface greatly reduces the areas on a part where corrosion can start, a key factor in improving performance.

In conclusion

Micro cracks, crevices, and other surface imperfections can weaken automotive parts that need to bend or flex, such as springs, hose clamps, and clips. This weakening occurs as a result of the notch effect and by increasing the potential for corrosion.

Electropolishing, an electrochemical process that removes a thin layer of metal from the surface of a part, produces a bright, shiny, uniformly smooth surface that eliminates cracks, crevices, and clinging particles that can cause premature part failure.

Able Electropolishing Co. Inc.
http://www.ableelectropolishing.com

About the author: Able Electropolishing Co. Inc. Vice President of Sales Scott Potter can be reached at scottp@ableelectropolishing.com.