Metal Surface Imperfections

Top engineers demand perfect surface finishes. What do they do when part of the machining process causes metal surface imperfections? One option that helps in a variety of situations is electropolishing.

Common Imperfections

Metal surface imperfections can happen in manufacturing for a variety of reasons. Most often imperfections happen as a result of an abrasive machining process. During the abrasive process a machining tool comes into contact with metal to remove materials and some of the material is left behind.

Burr —a metal imperfection characterized as a thin ridge of roughness left by cutting operations such as shearing, slitting, trimming, blanking, etc

Chatter—(metal) a series of traverse marks in the metal.

Dent—a mark transferred to a substrate surface from an imperfect process roll or something on a roll. The most common causes are tape, metal particles and dirt.

Metal marking—black or gray marks left on a painted strip when bare metal is drawn across its surface. White and light-colored coatings are more susceptible to metal marking than dark coatings. Metal marking typically occurs during forming operations.

Orange peel—a paint imperfection where the surface resembles the skin of an orange; also surface roughening on formed products resulting from the use of coarse-grained material.

Red rust elimination —residue from the corrosion of steel consisting of iron (ferric) oxide. The oxide is reddish in appearance (rust colored). Red rust may also manifest itself on galvanized steel. In this case, the protective zinc coating has been completely corroded exposing the underlying steel. Caused by the exposure of steel or iron to moisture.

Detection of Imperfections

As referenced by the variety of imperfections above, incorrect parts happen for many reasons. Many imperfection can be discovered with proper quality checking procedures. These types of procedures can be as advanced as looking through complex microscopes and can be as simple as spotting imperfections with plain eyesight. What is most important is that you have a system in place to catch imperfections and you know how to remedy them to a more perfect part.

How Does Electropolishing Cure Imperfections?

Electropolishing is a subtractive process which removes material from the service of your workpiece to create a smoother surface. Small burrs and imperfections are removed during the electropolishing process. Larger burrs produced in rough milling or displaced metal from drilling operations often need pretreatment using other methods.