Page 172 - Corrosion Engineering Principles and Practice

CHAPTER 6

Recognizing the

Forms of Corrosion

6.1 Recognizing Corrosion
The previous chapters provide an introduction to the general science
of corrosion processes with some practical applications. In reality, the
principles that govern these scientific concepts are rarely of interest to
people facing corrosion problems. The main questions generally
asked by most people facing a corrosion problem are
• How serious is this problem?
• How can it be fixed and how much will it cost?
• What caused the problem in the first place?

The present chapter will focus on answering the first of these
questions and Chap. 7 the last. The following quotation from Fontana
and Greene’s classic textbook on corrosion engineering originally
published in 1967 [1] summarizes a training principle that has been
reused extensively by many instructors and that is central in all
modern training manuals on the subject.
It is convenient to classify corrosion by the forms in which it manifests itself,
the basis for this classification being the appearance of the corroded metal.
Each form can be identified by mere visual observation. In most cases the
naked eye is sufficient, but sometimes magnification is helpful or required.
Valuable information for the solution of a corrosion problem can often be
obtained through careful observation of the corroded test specimens or failed
equipment.
It is now widely accepted that much can be deduced from
examination of materials which have failed in service and that it is
often possible by visual examination to decide which corrosion
mechanisms have been at work and what corrective measures are
required. In another widely used NACE document, Paul Dillon and

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