Energetica India Magazine - September 2022

energetica INDIA- September_2022 73 POWER SECTOR Formation of Zinc patina – which itself acts as a protective layer for the active zinc metal 3. Reasons for opting Hot Dipped Galvanization over Pre-Galvani- zation from Developers perspective i. Galvanization is the process of applying a protective zinc coat - ing to steel or iron to prevent corrosion. There may be various other ways of corrosion protection; however galvanized coat - ing is one of the most durable forms of corrosion protection. In an ideal condition i.e., without any operation loads on the steel structure i.e., if the galvanized steel is kept, with average coating thickness of 85 microns, it will protect the base material for al - most 100 years. It means, the galvanization is very durable. Hot dipped galvanization is proven and well-established meth - od. HDGmembers comes with guarantee of service life; however, Pre galvanized steel supplier do not provide performance guar - antee beyond 5 to 10 years. Scientific literature is present in case of HDG stating the year-on-year degradation of the coating in various corrosive environments, whereas no such data is avail- able for Pre-Gal material and the life of the asset is at risk beyond 10 years. ii. Hot Dipped Galvanization is almost maintenance free. Once it is done, there is no requirement of reapplication or recoating. Hot dipped Galvanization is very much sustainable. In case of pre galvanized material, after some service life the pre-galvanizedmaterial needs replacement and / or maintenance. iii. Indian solar developers are trying to increase the solar project life to 35-40 years instead of present standard of 25 years, and as most of the upcoming solar projects in India will be at C3-C4 corrosion zones, it is important to design the BOP systems for 40-50 years as well. Galvanization is techno – economically, cost effective solution when com - pared with grit blasted equivalent painting system. PU or alike painting systems must be applied in multiple layers over grit blasted steel surfaces. Usually painting scheme shall have 275 to 325micron thickness as per manufacturer prescription. However, this cost effectiveness is achievable in HDG only. Corresponding thickness of galvanization compared to 325micron painting is 60 to 80 microns. These 60 to 80 mi - crons of galvanization thickness provide minimum 25 to 30 years of life expectancy under worst condition like corro - sion condition greater than C4. Pre galvanizedmaterial does not provide the requisite thick - ness of galvanization and service life guarantee comparable with HDG and painting system. iv. Hot Dipped Galvanizing ensures complete coverage over steel surface, irrespective of it’s shape, geometry. As a pro - cess point of view, in case of hot dipped galvanization, once the structural member is completely fabricated including welding, punching, drilling, cutting etc. all operation, it is immersed into molten zinc and kept for requisite time du - ration. This ensures complete zinc coverage all over steel members. However, in case of pre galvanized steel members, this is not possible. The steel members which are fabricated using pre galvanized are highly susceptible to corrosion. In manufac - turing process of the pre-galvanized sheet (or similar prod - ucts), a bare steel plate of thickness is passed galvanization process. As a result, zinc coating is applied (of 20/30micron) only on the exposed surfaces.While fabricating the structur - al member to requisite shape and size it is subjected welding, punching, drilling, cutting i.e., all activities involved in fab - rication work exposes and damages the existing pre galva - nized layer., so corrosion starts and life of the steel structure member comprises. v. Hot Dipped Galvanizations provide superior abrasion resistance. In hot dip galvanization process, a zinc coating which is formed is firmly bonded metallurgically to the steel