Degradation of Materials (Corrosion) 9.1.Corrosion Mechanisms Despite the numerous useful properties of iron and steel and the cultural changes that came along with the introduction of iron, it has to be kept in mind that iron and steel are plagued by a grave detriment.This detriment is rusting,also often referred to by the generic and more accommodating names corrosion or environmental interaction.Specifically,rusting destroys goods valued at approximately 5%of the gross national product in in- dustrialized countries.Billions of dollars have to be spent annu- ally to replace or repair corrosion-related damages or to prevent corrosion.(About $250 billion per year in the United States alone.)Moreover,corrosion can weaken the strength of struc- tures made from iron and changes their appearance.It is of lit- tle consolation that many other materials such as glass and poly- mers likewise undergo some form of deterioration.Rusting transforms iron or ferrous alloys into ceramic compounds (e.g., iron into iron oxide or hydrated iron oxide),as we shall eluci- date momentarily.Actually,corrosion is a slow form of burning. In short,rusting is a prime destructive mechanism that affects a society which places its trust and investments into iron and steel. Many industrialists do not see these facts as just stated.For one,they consider the advantage of rusting to be that it creates a "repetitive market"for the goods which have been destroyed. This yields jobs for otherwise unemployed people and dividends for investors.Further,the usage of iron and steel is often an eco- nomic factor.Occasionally,replacing relatively inexpensive goods made of steel may be less costly than building equipment out of more durable materials that may cost several times more.9 Despite the numerous useful properties of iron and steel and the cultural changes that came along with the introduction of iron, it has to be kept in mind that iron and steel are plagued by a grave detriment. This detriment is rusting, also often referred to by the generic and more accommodating names corrosion or environmental interaction. Specifically, rusting destroys goods valued at approximately 5% of the gross national product in in￾dustrialized countries. Billions of dollars have to be spent annu￾ally to replace or repair corrosion-related damages or to prevent corrosion. (About $250 billion per year in the United States alone.) Moreover, corrosion can weaken the strength of struc￾tures made from iron and changes their appearance. It is of lit￾tle consolation that many other materials such as glass and poly￾mers likewise undergo some form of deterioration. Rusting transforms iron or ferrous alloys into ceramic compounds (e.g., iron into iron oxide or hydrated iron oxide), as we shall eluci￾date momentarily. Actually, corrosion is a slow form of burning. In short, rusting is a prime destructive mechanism that affects a society which places its trust and investments into iron and steel. Many industrialists do not see these facts as just stated. For one, they consider the advantage of rusting to be that it creates a “repetitive market” for the goods which have been destroyed. This yields jobs for otherwise unemployed people and dividends for investors. Further, the usage of iron and steel is often an eco￾nomic factor. Occasionally, replacing relatively inexpensive goods made of steel may be less costly than building equipment out of more durable materials that may cost several times more. Degradation of Materials (Corrosion) 9.1 • Corrosion Mechanisms