The thickness of a zinc coating is a common criterion for evaluating its projected service life. Essentially, the thicker the coating, the more service life it has. However, the thickness criteria can’t be used to compare zinc coatings generated by various methods.

Are you interested in learning more about coating weight and thickness? If so, continue reading below.

Understanding Coating Thickness

Understanding Coating Thickness

A magnetic depth gauge and optical microscopy are two ways of evaluating the zinc coating thickness of hot-dip galvanized steel. Because optical microscopy is a test method used solely to settle measurement conflicts, the easiest and non-destructive method is to use a magnetized thickness gauge.

Magnetic thickness gauges are available in three main types:

Pencil-sized Guages: This is a pencil-sized gauge that’s small enough to fit in your pocket and uses a spring magnet enclosed in a pencil-like container. Because the precision of the measurement is dependent on the inspector’s ability, it needs to be taken several times.

Banana Guages: Banana Gauges offer a benefit over pencil-style gauges in that they can determine coating thickness at any angle without needing to recalibrate or deal with gravity.

Electronic or Digital Gauges: The most exact and user-friendly gauge is the electronic or digital gauge. Electronic gauges also have the ability to store data and conduct averaging analyses.

The ASTM E376 standard describes how to quantify coating density with magnetic and electromagnetic gauges as precisely as possible. This includes how and where to make calculations and suggestions for decreasing mistakes. Among the most important requirements are:

  • Don’t take readings near a sharp edge, a pit, or inside a building.
  • On big objects, take measurements at least 4 inches from the edge.
  • If at all possible, avoid taking readings on curved surfaces.
  • Don’t take readings on the coating’s frequent locations.
  • Spread measurement readings out as much as they can.
  • To acquire a genuine value reflective of the sample, use at least five measurements.

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Understanding Coating Weight

Understanding Coating Weight

The quantity of hot-dip galvanized coating added to a product for a particular surface is referred to as coating weight. The coating weight of hot-dip galvanized steel measures in two distinct ways.

The first employs the weigh-galvanize-weigh method, which is only suitable for single samples. Weigh-galvanize-weigh is a method of determining the weight of a steel item after it’s treated and again after it’s galvanized.

This method only quantifies the zinc metal applied to the steel, which might result in a 10% underestimation of the overall coating weight.

The second approach, known as weigh-strip-weigh, is damaging and is only suitable for single samples. Weigh-strip-weigh determines the weight of a galvanized component after it has chilled and after the coating is stripped off using an acid solution.

Weighing Zinc Coating

Weighing Zinc Coating

Calculating coating weight vs thickness is a bit complex. But hopefully the info above helped you understand it better.

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