Erosion-Corrosion: An Introduction to Flow Induced Macro-Cell Corrosion

Erosion-corrosion is a generic name of degradation phenomena which occur on the chemical plant composing metallic materials under the conditions of various flowing liquids. For example, it occurs on heat transfer pipes of seawater heat exchangers (made of copper base alloys), casings of seawater pumps (made of gray cast iron) and carbon steel pipes which transport pure water of high temperature and pressure. Pipes made of carbon steel have sufficient strength and are simple and inexpensive to process. These are commonly used to transfer de-ionized water. Sudden and fatal explosion accidents have occurred in succession due to carbon steel pipes involved in high-temperature de-ionized water transport in thermal and nuclear power plants. The phenomenon was named FAC (flow accelerated corrosion) without the exact cause being clarified. It is a strongly suspected cause of the serious accident in 1986 with four victims which arose in the Surry nuclear power plant in Virginia, U.S.A.

Erosion-Corrosion is a compilation of nearly five decades of research on this theme throughout and demonstrates one true colour of this phenomenon; erosion-corrosions are not the product of the cooperation of erosion and corrosion, in which they may be generally believed, but are pure electrochemical corrosions in nature and usually occur in copper based alloys.

This e-book contains descriptions on erosion-corrosion testing methods and case studies carried out on the accidents which have occurred in the real chemical plants. Testing equipment helps us to estimate the erosion-corrosion damage in the laboratory and data of successive accidents in the field allows us to study the mechanisms behind it.

The mechanisms brought to light in this e-book are useful for predicting the site of incidence in chemical plants and the degree of the damage. In consequence, it is a useful tool for designing, material selection and maintenance of safer hydraulic machines and chemical plants, seawater pumps and piping in nuclear power plants.

Flow influenced materials degradation is encountered in many fields of our daily and technical experience, starting from rivers carving themselves into rock formations and finishing with severe wall thinning in metal pipes and pumps of industrial plants. Understanding the flow and materials related basic steps of initiation and continuation of such degradation processes has been subject of many research efforts in the last decades. This was often prompted by severe failures resulting in high financial losses and sometimes even fatalities. However, even today after all this work done so far in this field there is still a debate about how to describe the interactions between materials and flowing media in a proper and predictive way. It starts with the definition of terms used to classify different reasons for flow influenced materials attack: cavitation, erosion, corrosion, flow accelerated corrosion, etc. and combinations thereof. Worldwide, national and international standards give different definitions based on different views of the main influencing parameters.

This book starts with the intention not to add to this Babylonian confusion but to explain step by step the different phenomena and contribute to the understanding rather than verifying definitions of terms. This is one of the big merits of this book. The reader is firstly taken on an interesting travel through the historical approaches of research in cavitation, erosion and erosion corrosion which for many decades was significantly influenced by the author’s excellent and innovative work in this field. The somewhat narrative style in which the chapters are written keep the reader fascinated and eager to learn more about the experimental evidences for later conclusions. Many of the intelligent experimental devices and protocols for studying flow influenced materials degradation, presented and explained throughout the book, have been developed in the author’s research group over the years. I am proud to say at this place that they also inspired me some 20 years ago when I had the pleasure to meet Prof. Masanobu Matsumura in Germany. The exciting discussions we had at that time prompted us to design and produce jet impingement devices to study erosion corrosion phenomena electrochemically with jet impinged microelectrodes resulting in our “freak event” energy density theory for erosion corrosion initiation.

The book is an excellent summary of the great and path breaking research achievements of the author and his research group in the complex field of erosion corrosion and can only be warmly recommended for everyone who wants to understand the effect of influencing parameters in cavitation and erosion corrosion, alone and in combination with each other. It is an outstanding source of information for those who want to learn about erosion corrosion testing methods. Case studies underline and backup the technical importance of flow influenced corrosion in its various localized and wall thinning appearance and its threat for failures in industrial plants. The book fills a gap that has been open for too long time.

Günter Schmitt
Ceo Ifinkor
Institut fuer Instandhaltung und
Korrosionsschutztechnik gGmbH
Germany