|Project Name:||Evaluation and Removal of Surface Contaminants From Steel Prior to Coating|
Office of Infrastructure Research and Development |
|Team:||Bridge and Foundation Engineering Team|
Infrastructure Research and Technology Strategic Plan and Roadmap|
|Project Description:||Well-performing bridge coating systems are founded upon proper preparation prior to coating. Most coating systems require a near white metal blast-cleaned finish prior to the primer coat. However, there is a possibility for surface contamination from either not being removed during the blast cleaning operation or contaminated blast media, causing contamination. This project aims to understand what an acceptable level of contamination is prior to coating, identify what cleaning methods are required to achieve the acceptable level, and identify what means are necessary to measure the surface contaminant concentrations.|
Coatings and Corrosion Laboratory|
|Start Date:||August 1, 2011|
|End Date:||November 18, 2012|
The key project objectives are to:
(1) Identify effective means of measuring chloride, nitrate, and sulfate contamination on the surface of uncoated steel.
(2) Identify proper techniques for cleaning uncoated steel to a target level of contamination.
(3) Determine what levels of contamination are detrimental to bridge coating performance.
|Background Information:||In 1991, the Federal Highway Administration (FHWA) conducted a similar study summarized in a report entitled, "Effect of Surface Contaminants on Coating Life." However, the coatings industry has changed after 20 years and now there are newer field portable test kits to evaluate surface contaminants, as well as new coating systems. The 1991 study also identified that acceptable levels of contamination ranged from 20 to 50 micrograms per centimeter squared. This number is highly criticized for being too large as other industries limit surface contaminants to less than five micrograms per centimeter squared. Therefore, there is a need to reevaluate the acceptable levels of surface contamination and integrate the newest technologies for evaluating and achieving it.|
|Test Methodology:||laboratory evaluation|
|Expected Benefits:||The expected benefit is bridge coating performance that is more reliable and has a longer life cycle.|
Bridges and other structures|