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December 7 - December 11, 2020

What are the differences between an ethyl silicate base zinc-rich primer and an alkali silicate base zinc-rich primer? In what instances should one be used instead another?

Selected Answers

From Kalpesh Patel of Endura Manufacturing Co. Ltd. on December 10, 2020:
Weather you use ethyl silicate-based solvent borne zinc coating or alkali silicate-based waterborne zinc coating; end products are same in both which is Zinc silicate polymer and performs differently in a similar manner. Only difference is curing mechanism and different start off resins. Ethyl silicate solvent borne Zinc coating, the curing mechanism includes solvent evaporation and reaction between the zinc, air, and moisture to cure, it is fast dry, so recommended to use when early water resistance required, and early hardness is not important. While alkali silicates water borne zinc coating, the curing mechanism includes dehydration and reaction between the zinc, air carbon dioxide and moisture, it is recommended when early hardness, impact and abrasion resistance are required.

From Zenith Czora of Parex Davco on December 10, 2020:
Ethyl silicate base zinc- rich primer is solvent based that can be 2-pack or 1-pack components depending on the type ethyl silicate binder being used while the alkali silicate base zinc-rich primer is water based and a two- pack system. Both are formulated to be typically applied on steel surfaces that the hydrolysis reaction that occurs between the steel, zinc particles and the silicate binder produced a complex chemical structure which effectively became part of the steel surface. Essentially the silicate binder produced from the ethyl silicate reacting with water is similar to the silicate binder produced from waterborne alkali silicates, with ethanol being produced as a by-product rather than alkali carbonates. Solvent-borne ethyl silicate primer is fast curing, which after air drying for 20 to 30 minutes produce a coating which does not suffer from damage through exposure to early rain. Both primers provide long term corrosion protection of ferrous surfaces, however, the Zinc rich primer based on ethyl silicate is best in environment where there is exposure to severe weather and chemical and high temperature up to 400oC.

From Rob Francis of R A Francis Consulting on December 7, 2020:
Both have similar properties once cured, although the alkali water-borne (WB) is slightly harder. They have similar durability at the same thickness. The ethyl solvent-borne (SB) requires moisture to cure so should only be used if the humidity will be above 50% during application and initial drying. The WB requires good airflow and dry conditions to cure. If overcoated (best not to - use an epoxy zinc if allowed), the WB must be checked for alkali on the surface. For more differences, see my paper in Materials Performance, April 2016.

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Tagged categories: Asia Pacific; Coating Materials; EMEA (Europe, Middle East and Africa); Latin America; North America; Primers; Zinc; Zinc-rich (inorganic); Zinc-rich (organic)

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