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
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
The various processes for protecting steel from corrosion using zinc and their characteristics Hot Dip Galvanizing (General Galvanizing) A batch process in which prepared steel is immersed in molten zinc at around 450°C (galvanizing of fabricated articles in accordance with BS EN ISO 1461). A metallically bonded coating of zinc-iron alloy
The achievement of a quality hot dip galvanized coating, for general and architectural use, is dependent on many issues, some controllable and some not. This checklist addresses the issues that can be controlled by the designer and those controllable by the galvanizer. LEAD TIMES In the case of large contracts, the galvanizer
Staining and Discolouration of Galvanised Steel 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
Distortion & Warping During Galvanising 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
Protecting Threads During Galvanising 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
Renovation of Hot Dip Galvanised Steel 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
Hot Dip Galvanised Castings Galvanizing of castings is covered by EN ISO 1461:2009. 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
Welding Before and After Hot Dip Galvanizing A proportion of steelwork that is hot dip galvanized is subject to fabrication by welding prior to dipping. The welding process can affect galvanizing in terms of coating quality, distortion and creating an increased potential for cracking in isolated instances. By taking suitable actions
