Questions and Answers Regarding MCIs and Cathodic Protection (CP)
Question:
Is the MCI layer damaged by the current flow? Over what time?
Answer:
MCI is not damaged by cathodic current flow over time.
Question:
Does the reduced current caused by the MCI layer reduce the effectiveness of CP or improve it
by enabling it to function at a lower current for a given potential?
Answer:
MCIs are film-forming inhibitors. They are molecules, not ions. MCIs are dipoles, meaning they
are not charged, but have positive and negative areas within the molecule. Thus, they do not
participate in the current flow and that is why they do not adversely affect Cathodic Protection.
As Dubravka stated, (using a bridge for an example), you can use cathodic protection on a bridge
structure using CP for the columns and surface applied MCIs and/or CP to protect the arch and
beams. The application procedure would be:
1. Clean the concrete surface
2. Immediately apply surface applied MCIs
3. Apply CP paint
In this scenario, MCI provides protection to the rebar, but also provides protection to the metal
components in the CP paint through adsorption, hence the "double role" of MCI.