Research and Development Office

Coal Tar Enamel & Coal Tar Epoxy Materials Analysis and Performance History

Project ID: 1546
Principal Investigator: Bobbi Jo Merten
Research Topic: Repair and Maintenance
Funded Fiscal Years: 2015, 2016 and 2017
Keywords: aging infrastructure, coal tar enamel, coal tar epoxy, coatings, cost savings, maintenance planning

Research Question

What physical properties and/or chemical attributes caused coal tar enamel coatings to achieve extremely long service lifetimes? What are the physical properties and/or chemical attributes of coal tar epoxies that make their service lifetimes so much smaller than enamels?

The waterways of Reclamation powerplants were originally coated with coal tar enamel. The material has continued to provide corrosion protection for the underlying steel. In certain conditions, this service life has surpassed 80 years. Coal tar enamel was regulated out of use in the 1970's. Since then, epoxies, which are more expensive to purchase and apply, have been used as a replacement. The epoxy service lifetime is approximately to 20-30 years. This maintenance cycle for protecting aging infrastructure is not practical, nor is it affordable to Reclamation facilities. Additionally, environmental regulations may regulate out all use of any coal tar pitch in protective coatings.

This research project will evaluate coal tar enamel and coal tar epoxy coatings using the critical eye of 21st century coatings researchers. Furthermore, the material will be evaluated using state of the art techniques to identify the material characteristics leading to this successful barrier coating.

Need and Benefit

It is necessary to understand the attributes that made coal tar enamel a successful barrier coating in order to develop new, successful materials. This information will also be helpful to improve the epoxies that are currently being used as a replacement.

Coal tar enamel achieves achieves a 50 to 80(+) year service life, but can no longer be used due to several hazards. Today's commercial replacement coatings, including coal tar epoxy, average 20 to 30 years of service. These recoat operations are expensive, surpassing millions of dollars per penstock relining, and with a very small fraction of this total cost going toward the new coating material.

Reclamation will see benefits approaching $1 billion in the next centuries if this research leads to the development of safe, easy-to-apply, alternative coatings that restore our long-term maintenance cycle. These benefits also extend to other agencies including the US Army Corps of Engineers. The U.S. Army Corps of Engineers is currently specifying coal tar epoxy at their facilities.

A subsequent goal of this project is to make a significant advancement in the field of corrosion mitigation systems, particularly toward long-term coatings for immersion service. This will aid in achieving the recommendations published by the National Academy of Sciences 2011 report, "Research Opportunities in Corrosion Science and Engineering." The recommendation to be applied here is as follows: "Each agency and department should assume responsibility not only for supporting corrosion research but also for disseminating the results of the research."

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Coal Tar Enamel & Coal Tar Epoxy Materials Analysis and Performance History (final, PDF, 8.0MB)
By Bobbi Jo Merten
Research Product completed on September 30, 2017

Coal Tar Enamel & Coal Tar Epoxy Materials Analysis and Performance History (final, PDF, 8.0MB)
By Bobbi Jo Merten
Research Product completed on September 30, 2017

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