KnowledgeBase » Coating Thickness

ILZRO Classifications of Sandelin Steels

Research carried out by the University of Cardiff in Wales for ILZRO (International Lead Zinc Research Organization) project took an in-depth look at the problem of silicon reactivity and included phosphorous as a reactive element also. The researchers varied the weight percentage of silicon and phosphorous and then assessed the reactivity of the steel at different galvanizing temperatures. This work led to a table of reactivity clas...
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Coating Thickness vs. Coating Weight

The usual criterion for determining the expected service life of zinc coatings is thickness: the thicker the coating, the longer the service life. This is an acceptable criterion when comparing zinc coatings produced by the same process.When comparing zinc coatings produced by different processes, the thickness criterion cannot be used without considering the amount of available zinc per unit volume. It is also important to keep in mind...
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Why does the galvanized coating thickness depend on the steel thickness?

The hot-dip galvanized coating is an inter-metallic layer of iron and zinc, meaning the zinc and iron react and diffuse into one another to create the galvanized coating. If more iron is available to react with the zinc, a thicker coating can develop. Thicker pieces of steel tend to develop
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Can 4130 steel be successfully galvanized?

4130 steel is a chromoly steel. Steels of this chemistry have presented some adherence problems in the past when galvanized. The galvanized coating developed in some areas but not others. It would be best to try galvanizing a small sample of steel with this chemistry to determine the results before attempting to galvanize a large structure....
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Is it possible to have steel with chemistry too good for galvanizing?

It is possible to have steel chemistry with levels of silicon and phosphorus that are too low to meet the minimum thickness levels specified in ASTM A123 and ASTM A153. Very low silicon levels are seen more often on pipe though, not plate because aluminum is sometimes used as a deoxider rather than silicon. For steel with very low levels of silicon and/or phos...
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Why is lead added to the galvanizing bath?

Lead is not purposely added to galvanizing baths, rather it is an impurity in zinc. Different types of zinc have different levels of lead. The specified lead maximums for the various types of zinc can be found in ASTM B6. Lead does have the beneficial effect of decreasing the surface tension of zinc, which allows it to flow off the steel easier as it is being removed from the kettle. This creates thinner galvanized coatings that have l...
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Does magnesium chloride corrode galvanized steel?

Magnesium chloride can aggressively attack many types of steel, including galvanized steel. Wet magnesium chloride is more aggressive than dry. Magnesium chloride should not be left on galvanized steel for prolonged periods of time. Washing the galvanized steel with a dilute mild detergent and then rinsing with fresh water is sufficient for removing magnesium chloride. Detergents meant for aluminum should not be used on galvanized steel....
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Is there concern about galvanic corrosion when different types of zinc-coated steel are in contact?

There is not a concern of dissimilar metals corrosion (galvanic corrosion) when pairing zinc-coated steel of different types (for example when pairing a hot-dip galvanized bolt with a mechanically galvanized nut). Please be aware, however, that different zinc coatings offer different corrosion protection and service lives...
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What types of metals will not galvanize?

There are many types of materials that will not develop a galvanized coating. Iron is necessary for a galvanizing reaction to happen, so if you try galvanizing copper or aluminum, they will not develop a galvanized coating. 400-series stainless steel will not develop a galvanized coating either. Some types of chrome-moly steels can develop a galvanized coating, but will have many bare areas....
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Measuring Zinc Coating Thickness of Hot-dip Galvanized Steel

Coating thickness is tested by using a magnetic thickness gauge. There are three types of magnetic thickness gauges: pencil-style, banana-style, and electronic. Electronic thickness gauges are the most common and the most accurate. Information on how to measure the thickness with magnetic gauges is contained in ASTM E376, and the minimum coatin...
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