1.0 Introduction

Corrosion, mainly electrolytic corrosion, is a big problem and destroys every year thousands of tonnes of steel world wide.The principle possibilities of corrosion prevention are visibly at the schematic representation of a corrosion element, in this example with one iron cathode and zinc anode. 3 things, waters, oxygen and electrons, are needed at the same time at the cathode so that the cathode reaction can take place. If one component is missing, no corrosion takes place.

If water is missing, steel doesn't rust for example at dry air.

If oxygen is missing, steel doesn't rust for example in 100 m water depth.

If electrons are missing, steel doesn`t rust because the chemical reaction at the cathode can`t take place.

Electrons reach the cathode as ions through the electrolyte. If this way is blocked in the case of the representation for example by a glass top between anode and cathode, the corrosion electrical circuit is interrupted
and no corrosion of the zinc takes place. This is primarily the action of an anti-corrosion coating. It interrupts differently, depending on its quality, the connection between anode and cathode.

The determining quality of a corrosion prevention coating is to show a high electrical resistance in the corrosion current circuit.