Ask SSPC: Maintaining Surface Temperature on Steel Surfaces during Cold Weather

Every month, SSPC selects one of the many questions received through "Coatings Talk" or the SSPC Reference Desk and shares the response with visitors to SSPC Online. This month's inquiry, submitted on behalf of a customer by SSPC's Heather Bayne, concerns the challenges of maintaining steel surface temperatures in cold weather. Responses are from subscribers to "Coatings Talk," SSPC's email discussion list.

I had a discussion today about the challenges of maintaining the surface temperature of a steel surface in cold weather for a coating application. This is a major challenge facing us with the winter months approaching. Many times to assure a coating will cure properly in the cold temperatures it is necessary to heat the air where the steel substrate is to warm the steel. The temperature of the steel surface is important to avoid condensation and corrosion after abrasive blasting and to provide proper temperature for coating application and cure. As you can imagine this is not an easy task. Does anyone have any past experiences that address this issue?  Does anyone have "tips of the trade" to share?

Response from Coating Inspector

Several years ago I was on a job in the north. It was a new construction tank in December. The temperature was too cold to apply the paint on the inside of the structure. The decision was made to apply artificial heat via propane heaters. The end result was that the fuel gases created moisture and we ended up with ICE on the inside of the tank. Switching to outside heat and piping hot air into the tank we raised the temperature enough to install inside coatings. Apparently, heating the inside caused the ambient temperature to rise above the steel temperature, with the inevitable result that when temperatures fell, a dew point would be reached on inside and outside of tank.

Response from Coating Inspector

It depends greatly on the degree of cold temperatures that you are talking about. In Canada, the western prairie provinces will have many winter days with temperatures of -10°C to -28°C (-18°F to 14°F) or colder. The bottom line is, you have to build a hoarding or containment around the structure, creating an air space between the hoarding wall and the structure to be painted. You then proceed to heat the airspace, and if a tank, provide vented heat to the tank interior as well. Maintain air movement throughout the enclosure, and be aware of problematic heat sink areas such as floor plates and anything attached to concrete. Heating the tank interior only will not work in extreme cold conditions. An example of this would be the windshield of your car in winter. You can heat the car interior greatly, but the windshield temperature is still cold to the touch. The source of heat must be indirect fired heat, with combustion products vented well away from the structure, in order to prevent ice or frost buildup.  We have seen many coating failures, or coating discoloration due to the improper use direct-fired heaters. It would also be a good idea to have a full time " watch" to ensure your heat is not lost due to mechanical failure, loss of fuel, etc. Coating selection also plays a large part in ensuring a successful project. Use low temperature cure coatings whenever possible. You will also need much more heat than typical calculations will indicate.

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Disclaimer

These "Ask SSPC" columns are an account of activity on "Coatings Talk," SSPC's email discussion group, or of phone calls to SSPC Staff, and are intended to provide general information only. An evaluation of site specific conditions and/or circumstances by a protective coating specialist (e.g., SSPC PCS) is advisable before taking action. SSPC does not make any warranty or representation, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this account. SSPC does not assume any liabilities with respect to the use of or for damages resulting from the use of any information, apparatus, method, or process described.