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Proof of Concept for an Adhesion Measurement Device to Predict Overcoating Failures in the Field

Overcoating an existing bridge coating system can be an economical solution to maintain bridges.  Overcoating eliminates the costs for removal of old, often hazardous coating systems that were possibly applied years ago.  However, prior to the overcoating process, it is necessary to establish that the existing coating is well adhered to the substrate.  Coatings with inadequate adhesion must be removed.  Unfortunately, though some standard test methods are available, the determination of a well-adhered coating is not an exact science.   

Product Number: 41205-175-SG
Author: Moavin Islam, John Repp, James A. Ellor
Publication Date: 2005
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$20.00
$20.00

Overcoating an existing bridge coating system can be an economical solution to maintain bridges.  Overcoating eliminates the costs for removal of old, often hazardous coating systems that were possibly applied years ago.  However, prior to the overcoating process, it is necessary to establish that the existing coating is well adhered to the substrate.  Coatings with inadequate adhesion must be removed. Unfortunately, though some standard test methods are available, the determination of a well-adhered coating is not an exact science. It is well known that during the curing process some overcoat systems can develop a significant level of shear stress (i.e., stress acting tangential to the coating film) amounting to as much as 1300 psi. This stress, in combination with stresses due to structure vibration and thermal stresses can lead to the disbondment of the existing coating on the bridge structure.  Indeed, such a phenomenon is observed in practice and often within 1 to 2 years of completion of the overcoating project.

Overcoating an existing bridge coating system can be an economical solution to maintain bridges.  Overcoating eliminates the costs for removal of old, often hazardous coating systems that were possibly applied years ago.  However, prior to the overcoating process, it is necessary to establish that the existing coating is well adhered to the substrate.  Coatings with inadequate adhesion must be removed. Unfortunately, though some standard test methods are available, the determination of a well-adhered coating is not an exact science. It is well known that during the curing process some overcoat systems can develop a significant level of shear stress (i.e., stress acting tangential to the coating film) amounting to as much as 1300 psi. This stress, in combination with stresses due to structure vibration and thermal stresses can lead to the disbondment of the existing coating on the bridge structure.  Indeed, such a phenomenon is observed in practice and often within 1 to 2 years of completion of the overcoating project.

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