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Galvanizing Process
The galvanizing process involves immersing steel into molten zinc. The zinc reacts with the steel to form a series of zinc-iron layers. The zinc coating provides a very effective protection against corrosion even in underwater environments. Galvanized coatings are highly resistant to corrosion over a wide pH range, specifically between pH6 and pH12.5. In mains water of pH6 to pH8, calcium carbonate is normally present. This is precipitated onto the galvanized coating as a calcium carbonate scale that, together with zinc corrosion products, forms an impervious layer for an extended life expectancy. Typically, sheet up to 3mm thick is continuously galvanized at the mill. Sheet in excess of 4mm, including other items are hot dip galvanized giving a coat thickness of approximately 550g/m2 or 70mm.
Polyester Powder Coating
Powder coating is a superior finish that's found on hundreds of products you come in contact with each day. Powder is available in a wide variety of formulations, textures, gloss levels, and colours. Powder coating is an extremely attractive, scratch resistant, chemical resistant and durable. It's tough. It looks great. And it lasts a long, long time. Powder coating provides superior edge coverage. Since powder coated parts virtually have no drips, runs, or sags, the reject rate is very low.
Powder coating is an advanced method of applying a decorative and protective finish to a wide range materials and products. Powder coating is a dry finishing process. The powder used for the process is a mixture of finely ground particles of pigment and resin, which is sprayed onto a surface to be coated. The charged powder particles adhere to the electrically grounded surfaces until heated and fused into a smooth coating in a curing oven. The result is a high-quality finish.
Unlike most liquid coatings there are no solvents to evaporate in the powder coating process. This makes powder coating environmentally friendly. No paint sludge has to be disposed of because powder can be reclaimed and recycled, thus minimizing the impact on the environment.
Powder coatings on hot-dip galvanized steel provide an excellent corrosion resistant coating. The selection of this duplex system has two major attractions; the duplex system provides a high-grade architectural finish that does not contain any volatile material and the coating is particularly abrasion resistant. The powder coating is comprised of a polyester thermosetting resin that is applied to a clean galvanized surface and cured at temperatures near 350 0F (180 0C).
Wet Epoxy Coatings are often stipulated for projects in harsh corrosive environments where a standard galvanized or powder coated finish will not provide the corrosion protection required. Epoxy coatings provide the steel plate with an additional protective layers that act as a barrier to corrosive materials and consequently and extend project life. At your request APT will implement your specified painting system to meet your projects requirements. Steel surfaces require preparation, suitable products, application equipment and procedures to ensure good adhesion and minimise break down over time.
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