The document defines corrosion as the deterioration of a material due to a chemical reaction with its environment over time. It then provides definitions and examples of three common types of corrosion: uniform corrosion, galvanic corrosion, and concentration cell corrosion. Uniform corrosion is the most basic form, like rust, while galvanic corrosion occurs when different metals contact each other. Concentration cell corrosion happens when areas of a metal surface corrode at different rates due to differences in things like metal ion concentrations, oxygen levels, or protective coatings. The author intends to cover more types of corrosion in a future blog post.

1. By Robert Heidersbach
WhatisCorrosion?
PartOne

2. As an experienced engineer, forensic
consultant, and former professor with over
45 years in the fields of corrosion and
metallurgy, I often get the question:
What is corrosion?

3. According to the Kennedy Space Center, corrosion can be
defined as the deterioration of a material due to a chemical
reaction with its environment over time. Metals corrode
because they’re used in environments where they’re
naturally unstable, and it’s a big problem for bridge builders
and other architects who frequently use metal products in
their structures.
There are various forms of corrosion — can you believe
there are 15? Below is a selection of just three forms of
corrosion. More forms of corrosion will be included in my
next blog, “What is Corrosion? Part 2.”

4. According to the Kennedy Space Center, corrosion can be
defined as the deterioration of a material due to a chemical
reaction with its environment over time. Metals corrode
because they’re used in environments where they’re
naturally unstable, and it’s a big problem for bridge builders
and other architects who frequently use metal products in
their structures.
There are various forms of corrosion — can you believe
there are 15? Below is a selection of just three forms of
corrosion. More forms of corrosion will be included in my
next blog, “What is Corrosion? Part 2.”

5. U N I F O R M C O R R O S I O N
Let’s start with the basic form of corrosion first. You can
think of uniform corrosion as rust, since it is the most
common form of corrosion. And since rust is pretty
common, it’s not a huge issue for architects to take care of.
Using protective coatings like paint or a sealant can control
uniform corrosion.

6. G A L V A N I C C O R R O S I O N
Galvanic corrosion occurs when different metals come into
contact with each other. This form of corrosion can easily
be spotted where the two metals meet. Popular trinkets like
insulating gaskets and washers can assist with staving off
galvanic corrosion, but they will need to be replaced with
regular maintenance.

7. C O N C E N T R A T I O N C E L L
C O R R O S I O N
Concentration cell corrosion occurs when two or more
areas of a metal surface are in contact with each other, but
corrode at different rates. There are three general types of
concentration cell corrosion:

8. C O N C E N T R A T I O N C E L L
C O R R O S I O N
Metal Ion Concentration Cells: This happens most commonly in
water when a high concentration of metal ions are exposed
crevices and become corroded over time. This can be prevented
by sealing the exposed crevices to prevent water from coming
into contact with the metal.
Oxygen Concentration Cells: This type of corrosion can occur in
areas with low oxygen, like underneath wood, rubber, tape, and
other materials. This can be minimized by sealing the exposed
areas, keeping the surfaces clean, and avoiding materials that
will create moisture between surfaces.
Active-Passive Cells: Some metals actually depend on thin films
of corrosion product, called an active-passive cell, for corrosion
protection. If this thin film is broken, the metal beneath the film
will start to corrode. This type of corrosion can be avoided with
regular cleaning and application of protective coatings.

9. R O B E R T H E I D E R S B A C H
is the author of Metallurgy and Corrosion Control in Oil and Gas
Production. The book is based on Robert’s experience teaching new
engineers that need to understand metallurgy and corrosion control
in the oil industry. He is currently in the process of rewriting and
updating the publication, and welcomes any suggestions about how
to improve the book.