Q: We have a large balcony project and the Architect has requested that it be painted after Hot Dip Galvanizing. We have heard that most paint will not adhere directly to freshly galvanized steel. Is this true and how should we overcome this problem? A: In general most paints will not adhere to freshly galvanized […]
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It is common misconception that any zinc coating can be termed as galvanizing but this is in fact not the case as there are many different processes by which a zinc coating may be applied. Hot Dip Galvanizing refers only to coatings formed by immersing steelwork into molten zinc. However, there are two variations of
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Galvanized steelwork can be subject to staining and discolouration which can sometimes be mistaken for failure of the coating and rusting of the base steel. There are numerous reasons why such staining may take place and there are summaries below. Surface Contamination One of the most common causes of discolouration is general surface contamination with
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A duplex coating is defined as a combination of two different coating systems which often complement one another, Typically this means a metallic coating overcoated by an organic system. Examples of such systems are hot dip galvanizing surfaces which have been painted or powder coated. Typically, a galvanized coating on its own will provide adequate
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When galvanizing a steel article, it may be desirable to prevent a coating from forming in certain areas which will have special functions such as: A threaded component on a fabrication Drilled holes Surfaces which will be subject to welding after galvanizing There are several different methods that may be used to prevent a coating
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The galvanized coating applied by immersion in a bath containing molten zinc not only provides a high level of corrosion protection but is also very robust, such that it will normally withstand handling and erection. However, the coating may occasionally be subject to small areas of mechanical damage typically as chips at edges or corners
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Galvanizing of castings is covered by EN ISO 1461:2022. Hot dip galvanizing of cast iron provides excellent protection from corrosion and the coating is applied by immersion in molten zinc at 450°C forming a tough, adherent coating which is bonded to the base metal by series of zinc-iron alloy layers overlaid with free zinc. If
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Hot dip galvanizing provides a high level of corrosion protection due to the slow rate at which it corrodes in an atmospheric environment. Part of the protection is provided by a zinc carbonate patina, which forms on the galvanized surface over a period of time by reaction of atmospheric carbon dioxide with a thin layer
When two dissimilar metals come into direct contact and an electrolyte such as moisture is present, a battery cell is created and an electrical current flows. This causes the more electronegative or anodic metal as determined from the electro-chemical series (see below) to corrode more rapidly. This means that galvanizing being a zinc coating will
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In practice, cases of distortion during hot dip galvanizing are relatively infrequent. There are a number of important criteria that designers should keep in mind. Causes Distortion occurs due to the relief of locked-in stresses within a steel section or fabrication. At room temperature, the steel is sufficiently strong to accommodate such stresses, but at
Avoiding Distortion During Hot Dip Galvanizing Read More »
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