Adhesion Tool for Overcoating Risk-Reduction Analysis

摘要

Overcoating an existing bridge coating system can be an economical solution to maintain bridges. Overcoating eliminates the costs for coating removal of old, often hazardous paint systems that may have been applied decades ago. When applied to a properly prepared bridge, overcoating can extend the time between maintenance painting. Disbondment mechanisms in an overcoating project usually appear within one to two years after completion. These are often associated with a rapid change in temperature or are a side effect of the curing of the overcoating paint system. It has been theorized that shear stresses (stresses acting tangential to the coating film) cause the disbondment of the existing coating from the bridge substrate. An investigation of these stresses as a result of overcoating paint system cure was the focus of this research program. The specific objectives of this project were: (1) Identify the stress levels imparted during cure of overcoating systems; (2) Develop a device capable of evaluating coating adhesion using the stress levels identified; (3) Evaluate this device in a laboratory setting; and (4) Recommend how to implement the successful device as a standardized adhesion test tool.