Localised corrosion principles

Radioactivation Techniques Neutron and thin layer (TLA) activation are non-intrusive techniques ofi ering the prospect of continuous, direct component monitoring, in addition to coupon or probe, monitoring. In principle, localised corrosion can be monitored using a double-layer technique. Process plant applications of the technique have been limited to date. ... 

In Section 1.4 it was pointed out that a fundamental principle of corrosion is that the sum of the rates of the cathodic reactions must equal the sum of the rates of the anodic reactions, irrespective of whether the attack is uniform or localised ... 

Safe or dangerous inhibitors Each inhibitor must be present above a certain minimum concentration for it to be effective (see Principles), and this classification relates to the type of corrosion that will occur when the concentration is below the minimum, or critical, value. Thus, when present at insufficient concentration a safe inhibitor will allow only a uniform type of corrosion to proceed at a rate no greater than that obtaining in an uninhibited system, whereas a dangerous inhibitor will lead to enhanced localised attack, e.g. pitting, and so in many cases make the situation worse than in the absence of an inhibitor. 

---