Recondition or Overcoat?
The City of Isanti, Minnesota, has a 750,000-gallon water tower that was built in 2003, and has been considering either reconditioning or overcoating that tank. In 2017, Bolton & Menk assessed the tank, finding moderate rusting in the interior immersion areas and minor rusting on the exterior. By 2022, a follow-up inspection revealed minor to moderate corrosion, particularly at weld seams and structural steel support edges. The city faced two options: an exterior overcoat or complete removal and replacement of the coating system. The overcoat option involved spot repairs and a two-coat system, while the complete replacement included a three-coat zinc/epoxy/urethane system. The city chose the overcoat, starting the project in May 2023. The process required thorough surface preparation, including power washing, abrasive blasting, and applying a polyamidoamine primer. The project aimed to extend the tank’s service life while maintaining its appearance, with a tight schedule to ensure the city’s water supply remained uninterrupted.
The decision to opt for an overcoat was influenced by cost considerations and the tank’s current condition. The overcoat process involved detailed steps to ensure the longevity of the coating, such as using biodegradable detergents for cleaning and achieving a specific angular profile during abrasive blasting. The project also highlighted the importance of regular maintenance and monitoring to prevent extensive damage and ensure the tank’s functionality. The city’s proactive approach in assessing and addressing the tank’s condition has ultimately extended the life cycle of their assets.
Learn more about the considerations the city took into account for this project, and the final solutions for the tower in the May/June issue of the Journal of Protective Coatings & Linings.
Bolton & Menk’s team can support your next water storage, tower, and coating projects. Learn more on our Water & Wastewater Engineering page.
Authors:
Daniel Zienty is a Coating Specialist with Bolton & Menk, Inc., who has more than 25 years of industry experience. He holds a bachelor’s degree in construction technology from Purdue University and is a NACE-certified Coating Inspector, as well as an SSPC-certified Protective Coatings Specialist and Supervisor for Deleading Industrial Structures. He has received numerous Engineering Excellence Awards from the Consulting Engineers Council of Minnesota for his work on water tower restorations and has authored and presented related articles on protective coatings maintenance.
James Connor is a Senior Protective Coating Specialist and American Welding Society (AWS) certified Weld Inspector with Bolton & Menk, Inc., with more than 36 years of industry experience. Connor is also a certified Senior Coatings Inspector with the Association for Materials Protection and Performance (AMPP), and he has also served on the development committee for Bridge Component Standards with the American Institute of Steel Construction.
