Description
Known as the DUPLEX SYSTEM (GALVANIZED + POWDER COATED), the combination of two corrosion protection systems that complement each other:
- Galvanised coating
- Paint coating
The system consists of hot-dip galvanising the steel before applying a layer of powder coating.
Hot-dip galvanising is a corrosion protection procedure for materials and items made of iron or steel, which consists of dipping them into a bath of molten zinc. During this process, protective zinc coatings and zinc alloys are formed on these materials, which adhere perfectly to the base substrate through metallurgical bonding.
In the powder coating process, powder paint is especially developed to provide high corrosion and UV resistance as well as great mechanical strength.
The duplex system is generally used where more effective corrosion protection is required.
The most common examples are in building, urban furniture, road equipment, and chemical and electrical industries.
Main benefit: Long lasting protection
The main reason is the long lasting protection which, along with its attractive finish, is recommended for application in engineering works.
The duration provided by these duplex systems is typically much longer than the sum of the expected durations of each individual system. It can be said that there is a synergistic effect, which could be mathematically expressed using the following formula:
Where:
DT = Total duration of galvanising + powder coating
DZn = Duration of galvanised coating
DP =Paint duration
K = A constant
The synergistic effect, the value of the constant K, can be quantified between 1.3 and 2.5 depending on the paint system and the environmental conditions to which the system is exposed.
Because this coat of paint in turn protects the galvanised coating from the corrosive action of the atmosphere and chemical agents, it can be said that there is reciprocal protection which benefits both protection systems and which means that the duplex system last longer than would be expected from the sum of the foreseeable durations of each individual system.
Industrial application of powder organic coatings to hot dip galvanized or sherardized steel articles [duplex systems]. Specifications, recommendations and guidelines.
Process applied based on European quality mark QUALISTEELCOAT
Paints and varnishes. Corrosion protection of steel structures by protective paint systems. Part 5: Protective paint systems. (ISO 12944-5:2019).
Hot dip galvanized coatings on iron and steel articles. Specifications and test methods. (ISO 1461:2009)
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