Type I pitting

A higher content of AI2O3 and SiOj is critical for the composition of the protective films in the tubing, assuming the water contains silicates or silicic acid. The protective films have a maximum thickness of 1.5 mm and cannot grow further. The corrosion process can be stopped even in copper pipe networks with type I pitting [21] by providing a reaction tank with impressed current aluminum anodes. 

Type I pitting is associated with hard or moderately hard waters with a pH between 7 and 7.8, and it is most likely to occur in cold water. The pitting is deep and narrow, and results in pipe failure (Fig. 6.12). 

When I carried out my first corrosion investigation, some 25 years ago, on what turned out to be a 90-10 copper-nickel tubing Type I pitting problem it never occurred to me that this was indeed to trigger an important transition in my career. Well, that seems to be how many corrosion engineers have stumbled onto what was later to become a central focus of their work. There are many reasons for this. One common factor that often attracts an investigator s attention is the drastic contrast that exists between the importance and seriousness of a corrosion problem and the size of the damage itself. 

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