In 1742, a chemist named Melouin presented a paper to the French Royal Academy in which he described how a zinc coating could be obtained on iron by dipping it in molten zinc.
However, it was not until the 1830's that patents were taken out in England and France covering this process for protecting iron from rust. More than 150 years on, applications for hot dip galvanizing continue to grow and it has become part of every day life.
It is environmentally friendly, aesthetically pleasing and helps save our natural resources by protecting steel from the damaging effects of corrosion.
Galvanizing is a term often used to describe zinc coatings in general. However, different types of zinc coating vary in thickness and effectiveness. It is therefore important to understand that all zinc coatings are not the same and the life of a zinc coating is directly proportional to its thickness.
Hot dip galvanizing after fabrication provides the best long term corrosion protection for steel products achieved through a continuous and extremely tough metallurgically bonded coating which offers both barrier and sacrificial protection. The zinc coating reacts with the atmosphere to form a thin, passive zinc oxide layer which then protects the surface from further corrosion. Even if the zinc layer is damaged, the zinc corrodes in preference to the underlying steel and heals itself around the point of damage.
This is in stark contrast to paint coatings or other metal coatings such as nickel or chrome. Here accelerated corrosion of the underlying steel takes place around the damaged area.
From time to time you may have a requirement for galvanizing items which may be unsuitable for conventional dipping. Perhaps they have no hanging holes, are very small or have threads or small holes which must be kept clean and clear during galvanizing.
We offer a centrifuge galvanizing service which is particularly suitable for larger quanities of small components and threaded fasteners.
CENTRIFUGE GALVANIZING MAXIMUM LENGTH - 600mm
For further advice on centrifuge galvanizing please contact our technical department.
Before we galvanize your work, it is dipped in hydrochloric acid and pickled. This process chemically cleans the work to enable the galvanizing to take place. Pickling will remove mill scale, light rust and dirt but certain types of surface contamination will not be removed and if present will result in processing delays and /or a poor quality coating. The following surface contaminations will cause problems and should be removed before work is sent to us for galvanizing.
- Old zinc coatings- it is not possible to galvanize over an existing galvanized coating. In this case the old coating must be removed. Stripping and re-galvanizing can be an expensive and time consuming process and is best avoided if possible.
- Oil based paints - including over-spray, colour coding marks, stockholders identification marks.
- Oil and Grease- including grease on box sections and lubricants used for punching and drilling.
- Anti-splatter sprays- avoid using oil and silicon based products. Use only water soluble solution and use them sparingly.
- Lacquer - often found on pipe work and fittings.
- Weld slag and Sticky labels