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November 16 - November 20, 2020

How long can a blasted surface be left before priming under different temperatures/relative humidity environments?


Selected Answers

From Jaime Marcos of Profesional independiente on November 24, 2020:
The prepared surface should be painted as soon as possible, depending on the environmental conditions, and to avoid contamination. In conditions of surface temperature greater than 3ºC above the dew point (Ts> 3ºC + Dp) and relative humidity less than 85%, the surface must be painted within 4 hours. Dehumidifiers and heaters are used inside tanks to maintain environmental conditions of relative humidity less than 60% and surface temperature greater than 3ºC above the dew point, which allows several days without painting, until finishing the surface preparation of everything the tank. In any case, you must follow the manufacturer's recommendations indicated in the Technical Data Sheet of the paint.

From robert richter of Chlor-rid on November 19, 2020:
Depends on so many variables. Biogenic and anthropogenic surface contamination (Soluble salts), atmospheric deposition and conditions. Can vary day to day week to week. Use of alkaline or acidic surface treatments can extend the time before the substrate fails.

From S.SANKARA NARAYANAN. of SWATANTRAYA CONSULTANTANCY. on November 19, 2020:
It is advisable and customise to apply one coat of anti corrosive primer to freshly blasted surfaces with minimum time interval of the said operation (Blasting) as the surfaces becomes highly active towards oxidation irrespective of the external factors. The ensuing primer coating will arrest the phnomenan of corrosion and stops flash rust. Thank you so much and awaiting eagerly for OTHER EXPERTS OPPINIONS!

From Tom Schwerdt of TxDOT on November 18, 2020:
Until the surface no longer meets the specified requirements.

From Thomas W. Neal of KTA-Tator, Inc. on November 18, 2020:
There is not one magic answer to this question. The ambient conditions as well as the starting condition of the steel and the coating requirements will dictate this time. The surface will resist turning a lot longer in a dry climate versus a humid one. Surfaces inside of containment will resist turning longer than one exposed to outside air generally but if the blasted surface was chloride contaminated, then this time will likely change. Basically,tt is all about the dew point. Even when a time limit is stated in specifications, there is usually a statement that surfaces must be primed before rust bloom occurs. Hence, more frequent ambient condition readings are needed in deteriorating ambient conditions in an attempt to keep ahead of any rust bloom.

From Tony Bochniak of Ascend Build on November 17, 2020:
This is a tricky question. Provided that there are no anti-corrosion additives used, it should be coated asap, but for sure within the same day. Needs to be coated before any rust bloom occurs.

From Jaime Marcos of Profesional independiente on November 17, 2020:
The prepared surface should be painted as soon as possible, depending on the environmental conditions, and to avoid contamination. In conditions of surface temperature greater than 3ºC above the dew point (Ts> 3ºC + Dp) and relative humidity less than 85%, the surface must be painted within 4 hours. Dehumidifiers and heaters are used inside tanks to maintain environmental conditions of relative humidity less than 60% and surface temperature greater than 3ºC above the dew point, which allows several days without painting, until finishing the surface preparation of everything the tank. In any case, you must follow the manufacturer's recommendations indicated in the Technical Data Sheet of the paint.

From Jaime Marcos of Profesional independiente on November 17, 2020:
The prepared surface should be painted as soon as possible, depending on the environmental conditions, and to avoid contamination. In conditions of surface temperature greater than 3ºC above the dew point (Ts> 3ºC + Dp) and relative humidity less than 85%, the surface must be painted within 4 hours. Dehumidifiers and heaters are used inside tanks to maintain environmental conditions of relative humidity less than 60% and surface temperature greater than 3ºC above the dew point, which allows several days without painting, until finishing the surface preparation of everything the tank. In any case, you must follow the manufacturer's recommendations indicated in the Technical Data Sheet of the paint.

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Tagged categories: Asia Pacific; EMEA (Europe, Middle East and Africa); Humidity and moisture; Latin America; North America; Surface Preparation


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