hot dip galvanizing
What is hot dip galvanizing?
Hot dip galvanizing is a metallurgical bonding of zinc to steel performed in controlled conditions in a factory setting. This simple process is characterized by exceptional corrosion resistance, thanks to molecular adhesion of the two metals as well as cathodic protection.
DAMAGED PAINT COATING VERSUS GALVANIZING
The image above shows the difference between painting and galvanizing when the coating is damaged. It is readily apparent that while rust quickly spreads below the paint, zinc covers the damaged area.
Service life of a galvanized trailer
Since galvanizing is more than just a coating, the thickness of the zinc alloyed to the steel affects service life. Zinc thickness is a function of steel chemistry and its physical properties. For the small trailers, zinc thickness is 3 mils; for the big ones (dumper and +), it’s 4 mils.
Environmental factors and road contaminants also affect service life. Like any vehicle, regular washing, particularly during winter when deicing salt is used, will greatly extend the life of your trailer.
Why does zinc go from silver to a grey colour?
Zinc becomes more stable over a period of approximately 18 months. As it passivates, it darkens and becomes even more durable.
As well, differences in steel chemistry can affect the brightness and colour of a newly galvanized trailer. A yellowish colour may also be present, a byproduct of a process that enhances the passivation of the zinc. All these variances are temporary in nature and will disappear over time.
Why is the surface texture of zinc not always uniform?
The galvanizing process is performed by dipping the entire trailer in pure molten zinc. This insures complete protection inside and outside every tube. The complex shape of trailers means that some variation in the surfaces related to drainage is unavoidable. It is therefore normal to see mottled surfaces and/or small accumulations of zinc in closed areas.
Is it normal to have white powder on the zinc surface?
Whitish powder deposits are in effect oxides of zinc. The oxidation of zinc is how zinc pasivates itself and thereby becomes even more durable.
This last step leaves a very resistant patina that protects the pure zinc below. Humidity, precipitation and environmental contaminants like deicing salts can accelerate the process but are not harmful so long as the trailer is regularly exposed to fresh air.