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November 18 - November 22, 2019

What surface treatment is best when the maximum manufacturer recommended interval for overcoating has been exceeded?

Selected Answers

From Kalpesh Patel of Endura Manufacturing Co. Ltd. on November 21, 2019:
Depends on type of coatings: some coatings are softened by the solvents in the paint that is going to be used as a second coat. Some high performance coatings needs to be abraded  mechanically or chemically. Most coating manufacturers have this information on their technical data sheets.

From Tom Schwerdt of TxDOT on November 21, 2019:
Read the manufacturer's instructions for overcoating after exceeding the recoat interval.

From maxim dube of Galvatech2000 on November 19, 2019:
Most of the time, if the maximum recoat times have been exceeded, the surface must be abraded by sweep blasting or sanding prior to the application of additional coats. But always refer to the paint manufacturer to make sure what they specify.

From Neil Pittman of Lake Superior Consulting on November 19, 2019:
Check with the coating manufacturer!

From Aajjay Sunkay of ASSETREIFURB ENGINEERRS on November 18, 2019:
Once overcoating time is exceeded, then the coating surface becomes inert and chemical adhesion between layers become inactive. Hence, the coating surface is to be treated  like a bare metal surface, which needs profile for mechanical adhesion. Hence, the coating surface is to be abrade mechanically by wire brushing or grinding to have rough profile . For large surfaces, the surface is to be sweep-blasted to have mechanical key for adhesion. There is also the option to activate the surface chemically by use of styrene monomer for polyester or vinylester resin-based coating, but for epoxy resin-based coating, there are limitations for activating the surface chemically. The best way is to contact the coating manufacturer for the chemical to be used for activation. Otherwise,  use of a chemical to reactivate the surface may impair the chemical resistance property of  thecoating applied.

From CharlesE (Mac) McKenna of SERES on November 18, 2019:
Chemically or mechanically reactivate the surface.

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Tagged categories: Coating Application; Overcoating

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