page_title: Corrosion
section_title: Applied coatings
hierarchical_section_title: Corrosion / Protection from corrosion / Surface treatments / Applied coatings
caption_attribution_description: Deutsch: Feuerverzinkte Oberfläche eines Nagelbinder mit dem charakteristischen Eisblumenmuster English: A galvanized surface (a steel "strong-tie" joiner) showing visible spangle (of approx. 5mm).
context_page_description: Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, or sulfide. It is the gradual destruction of materials by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and preventing corrosion.
  In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen or sulfates. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide or salt of the original metal and results in a distinctive orange colouration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases.
  Many structural alloys corrode merely from exposure to moisture in air, but the process can be strongly affected by exposure to certain substances.
context_section_description: Plating, painting, and the application of enamel are the most common anti-corrosion treatments. They work by providing a barrier of corrosion-resistant material between the damaging environment and the structural material. Aside from cosmetic and manufacturing issues, there may be tradeoffs in mechanical flexibility versus resistance to abrasion and high temperature. Platings usually fail only in small sections, but if the plating is more noble than the substrate (for example, chromium on steel), a galvanic couple will cause any exposed area to corrode much more rapidly than an unplated surface would. For this reason, it is often wise to plate with active metal such as zinc or cadmium. If the zinc coating is not thick enough the surface soon becomes unsightly with rusting obvious. The design life is directly related to the metal coating thickness. 
  Painting either by roller or brush is more desirable for tight spaces; spray would be better for larger coating areas such as steel decks and waterfront applications. Flexible polyurethane coatings, like Durabak-M26 for example, can provide an anti-corrosive seal with a highly durable slip resistant membrane. Painted coatings are relatively easy to apply and have fast drying times although temperature and humidity may cause dry times to vary.
  Nowadays, organic coatings made using petroleum based polymer are being replaced with many renewable source based organic coatings. Among various vehicles or binders, polyurethanes are the most explored polymer in such a attempts.
caption: Galvanized surface
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