Evaluation of a Chemical Humectant Applied to an Existing Metallized ZincCathodic Protection System

摘要

This project documents the application of a humectant chemical to an existingmetallized zinc cathodic protection system at the Yuba Pass Separation and Overhead (03-NEV-80-KP-R95.65). The cathodic protection system has been in operation since 1994, but has not achieved performance standards in accordance with criteria of the National Association of Corrosion Engineers (NACE). The metallized zinc cathodic protection system has not been able to shift the potential electronegatively 100 mV from the native potential. Since the system has not achieved NACE standards, corrosion of the reinforcing steel has not been halted. Caltrans has reached the conclusion that effective cathodic protection polarization has not been achieved because the electrical resistance at the zinc/concrete interface is sufficiently high, such that not enough current is conducted from the zinc anode to the reinforcing steel. The purpose of this research project is to evaluate the effectiveness of a chemical humectant to improve the performance of the existing cathodic protection system. It is theorized that the humectant, which is hygroscopic, will attract moisture from the air to the zinc/concrete interface. As a result, the resistance of the zinc/concrete interface should be reduced, cathodic protection current should increase, and polarization of the reinforcing steel should improve.