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February 7 - February 13, 2016

Is a sealer coat always required for coating systems applied to concrete surfaces that will be exposed to marine environments?

Selected Answers

From shafeek parokkot of builtech engg on May 9, 2016:
Stephen Bothello: well explained, sir. 

From Mario Colica of Colimet srl on February 12, 2016:
Sealers do not solve the problem. I'd better refer to the decision taken by the New Jersey Department of Transportation in 2001 to use pure zinc metallizing .The metallizing work was performed off-site and no rust problems appeared until now.

Concrete is a porous material that readily absorbs liquids. In freeze-thaw climates, the expansion of frozen liquids can destroy the surface of unsealed concrete. Oil, salt and other chemicals can discolor and damage unsealed concrete.We must apply the sealer coat to prevent  premature failure.

From Stephen Bothello of Jotun UAE Ltd on February 7, 2016:
The main factors influencing durability of concrete in a marine environment are a) porosity, which is an intrinsic property of concrete (interconnected pores); b) exposure to aggressive elements present in sea water, namely chlorides, sulfides and alkali ions; and c) exposure to external environmental water (with dissolved salts). If any one of these factors is absent, deterioration of concrete will not occur. Protective coatings applied well over concrete will function to protect the concrete by forming an effective physical barrier to salts, chemicals and external water, thereby enhancing the durability of the structure. However, many coatings due to their design limitations (wetting and penetration properties), will not penetrate into the porosity of concrete and are restricted to physical bonding at the surface level. Also, such coatings applied directly over unsealed concrete will tend to exhibit numerous coating application defects like pinholes and bug-holes that may further lead to premature coating failures like blistering and delamination of the coating, exposing the concrete to marine environment and finally affecting the durability of the structure. Concrete sealers are essentially low viscosity polymeric coating materials with good flow, wetting and penetration properties. Due to the low viscosity profile (achieved either by way of low molecular weight polymer or/and dilution by solvents), they are absorbed by concrete and penetrate deep into its porosities. Certain sealers (silicates) are reactive and block the porosities at the surface, while others (siloxanes) accomplish water repellent/ hydrophobic properties at the surface (eliminating or reducing external environmental water. Epoxy/ urethane sealers will impart high chemical resistance. As per the name, sealers are intended to penetrate into surface pores of concrete and seal the pores. Sealers also function as a tie-coat to accomplish an adhesive bonding between the concrete substrate and further compatible protective coatings.. As of now, we can say sealers are essential for most, if not all coating systems exposed to marine environments.

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Tagged categories: Asia Pacific; Coating Materials; Concrete; Concrete coatings and treatments; EMEA (Europe, Middle East and Africa); Latin America; Marine Coatings; North America; Sealers

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