Which type of zinc is known to provide limited cathodic protection?

Zinc (Organic) is known to provide limited cathodic protection primarily because of its composition and the way it interacts with the environment. In organic coatings that contain zinc particles, the cathodic protection is not as extensive or effective compared to inorganic zinc coatings. This is because organic binders can limit the exposure of the zinc to the cathodic reaction, thus inhibiting its ability to offer robust protection against corrosion. The organic variety may be used for aesthetic purposes or to provide some corrosion resistance, but it doesn't achieve the same levels of cathodic protection characteristic of inorganic zinc systems.

In contrast, inorganic zinc coatings are specifically formulated to maximize cathodic protection due to their high conductivity and the electrochemical properties of zinc. Zinc oxide does not provide cathodic protection in the same sense as zinc metal since it is a corrosion product and tends to be non-protective in terms of galvanic action. Zinc alloys might have different protective qualities depending on their composition and the specific application, but they typically do not offer the same level of cathodic protection as pure zinc. By understanding the unique characteristics of organic zinc in relation to cathodic protection, one can appreciate why it is considered to provide limited efficacy in protecting against corrosion.