Anode performance: The use of ballasted mixed metal oxide coated titanium anodes in impressed current systems installed within historic steel frame masonry clad structures

摘要

Corrosion damage in historic steel frame structures has a great physical and financial impact on the performance and treatment of the building facade. Minor cracking and displacement of masonry can eventually lead to spalling and loss of stones and, as seen in rare instances, the loss of life if large masonry units become dislodge and fall from great heights due to corroding steel supports. Cathodic Protection is a corrosion mitigation technique, which minimizes stripping of the masonry while simultaneously protecting the steel from corroding. The core philosophy for the use of Impressed Current Cathodic Protection (ICCP) in historic buildings is to protect cultural heritage from the ravages of corrosion and the designer's scope is meant to follow conservation guidelines. This approach anticipates that no additional harm will be incurred by a building upon or after installation of a system. For this reason, the appropriate anode must be utilized within the parameters of the structure. It is critical that electrochemical reactions be minimized at the surface of the masonry. The reaction can have dire consequences on historic masonry, not only deteriorating the mortar, but dissolving limestone or cast stone in the correct circumstances. The designers' role is to recommend the best anode system for the subject building. The use of ballast anodes within these circumstances have led to better overall performance of ICCP Systems in Historic Steel Frame Structures. The paper will look at two case studies where different ballast anodes types were installed within historic steel frame structures, and discuss the benefits of the Ballast resistors.