There are mainly two commonly adopted criteria for controlling CP. One is the polarized potential criterion and the other one is the polarization shift criterion1. These criteria are not the true criterion for cathodic protection; they are the surrogate criteria (see below). The polarized potential criterion is to control the instant-off structure-to-electrolyte potential within a specified range. For example, the instant-off potential should be between -0.85 and -1.2 V vs Cu/CuSO₄ (V_CSE) for pipelines buried in soil. The polarization shift criterion is to control the polarization of a CP-protected structure to a given minimum value and this minimum value is usually 100 mV. The polarization is determined either by the difference between the corrosion potential of the structure measured before CP is applied and the instant-off structure-to-electrolyte potential, or by the difference between the depolarized potential of the structure and the instant-off structure-to-electrolyte potential.

Metallic corrosion is a natural inevitable phenomenon defined commonly as the deterioration of metals due to reactions with their environments. The global cost of corrosion estimated by NACE in 2013 was found to be $2.5 trillion (USD), which is approximately 3.4% of the global gross domestic product (GDP). The two-year global study released at the CORROSION 2016 conference in Vancouver, B.C., Canada, assessed the economics of corrosion and the role of corrosion management in establishing best practices for the different industrial sectors. It found that implementing corrosion prevention best practices could result in global annual savings of 15-35 % of the cost of damage, which is equivalent to $375-875 billion (USD). These estimations excluded the cost of individual safety and environmental consequences from corrosion. Corrosion mitigation has been extensively researched. The methods of corrosion prevention include, but are not limited to, selection of the right material of construction, coatings, corrosion inhibitors, and cathodic protection.^1,2