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10. Maintenance of hot dipped Galvanised Product
The following information offers some guidance on the general care and maintenance of hot dip
galvanized steel products.
Avoid long periods of exposure of your galvanized steel product to environments where the pH
is below 6 and above 12. Outside the range of pH 6-12 the galvanized coating can suffer greater
corrosion than normal.
Avoid direct contact of your galvanized steel product with dissimilar metals, such as brass and
copper, particularly in corrosive environments. Where dissimilar metals are to be used together
ensure that there is an insulator between the dissimilar metal and the galvanized product.
Do not constantly abrade clean your galvanized product and, where possible, avoid abrasive
washing of your galvanized product altogether. One of the ways in which galvanizing protects
steel from corrosion is by the development of a thin barrier film of insoluble zinc corrosion
products (known as a patina) on the outer surface of the galvanized steel through exposure to
the atmosphere. Abrasive cleaning will wash away this protective patina and the galvanized
article will have to build up this barrier protection again, consuming more of the zinc. Constant
abrasive cleaning will consume the zinc more quickly and therefore may reduce the life of your
galvanized steel product.
Galvanizing may be cleaned using a water-based emulsifier, alkaline-based cleaners with a pH
of 12 or lower or organic solvents. Then rinse the area with fresh water and simply wipe clean
with a soft cloth.
For galvanizing products that are situated in a highly corrosive environment e.g. coastal, heavy
industrial, etc. it is recommended the product be rinsed with potable water on a regular basis,
particularly under sheltered conditions (i.e. not exposed to rain and sun).
Avoid long term storage of any galvanized product in damp and poorly ventilated
conditions. Ensure the storage location is dry and there is effective ventilation.
If there is physical damage to the galvanized coating of the product (e.g. coating is chipped or
fabrication after galvanizing has taken place), it is recommended that the damaged area be
repaired in accordance with the procedure below.
There are a number of ways of treating different types of stains or marks. It is advised that with
any of the cleaning treatment of the galvanizing should be conservative at first and then if the
situation demands, the treatment can become steadily more aggressive. It is also important that
wherever some form of mechanical abrasion or “scrubbing” is required, a hard plastic bristle
brush is recommended to be used. Steel bristle brushes are not to be used since they will cause
discolouration.
It is important to note that mechanical methods of cleaning zinc surfaces can cause aesthetic
issues. The “cleaned” areas are likely to contrast with adjacent untreated surfaces and may take
a significant period of time to weather to a uniform colour. If aesthetics is a large concern, it is
advisable to first test the cleaning method in an inconspicuous area in case the aesthetic effect is
unappealing.
For general cleaning of bulk contaminants such as dirt and the like, ordinary laundry soaps can
be satisfactorily used. For more stubborn or larger areas, the use of a low pressure wash (such as
a pressure washer), with just pure water or in conjunction with proprietary cleaning materials
such as car wash or truck wash, can be effective.