Corrosion can often be predictable or it can be totally unpredictable and catastrophic, such as the hydrogen embrittlement or stress corrosion of critical structural members and pressure vessels in the aerospace and chemical processing industries.
Corrosion is affected by the properties of both the metal or alloy and the environment.
The concept of pH is complex. It is related to, but not synonymous with, hydrogen concentration or amount of acid. While corrosion obeys well-known laws of electrochemistry and thermodynamics, many variables that influence the behavior of a metal in its environment can result in accelerated corrosion or failure in one case and complete protection in another, similar case. Avoiding detrimental corrosion requires the interdisciplinary approach of the designer, the metallurgist, and the chemist. Sooner or later, nearly everyone in these fields will be faced with major corrosion issues.