Liberty Intercept Blog

Consider this statement on corrosion from the Government Accountability Office in 2011:

“Corrosion destroys equipment, decreasing readiness and reliability while causing safety hazards and increasing maintenance and other ownership costs. The Department of Defense (DoD) estimates corrosion costs the department over $23 billion annually.”

This is sixth in a series on Corrosion Control. Find the previous articles here.

After talking about cathodic protection, and specifically some of the more complex impressed current cathodic protection systems, we now come to seemingly the most boring of the subsections of corrosion control: materials selection. However mundane choosing materials may seem (or may even actually be), it is, in fact, the most important factor in corrosion control. To be sure, there is an entire universe of materials selection for corrosion control. Several (possibly leather-bound) books have tried to illuminate areas of common concern, the most comprehensive being ASM International's Materials Selection for Corrosion Control by S.L. Chawla and R.K. Gupta. Although in the 24 years since that book was published, not only has the science of corrosion control developed, but the number of materials from which to select has also grown. An update may be needed, but this article shall not suffice for that job, it shall merely overview the subject.

This is fifth in a series on corrosion control; find the other posts here.

Corrosion inhibitors is a bit of an unfortunate term. One could rightly suggest that the entirety of corrosion control is focused on inhibiting corrosion, so any technique used within that umbrella could be called a corrosion inhibitor. Within the corrosion industry (yes, it is a proper industry), corrosion inhibitor refers to chemicals which are applied in low concentration, and which act in one or more of three ways:

Since the evolution of the homo sapiens brain, individuals blessed with such a biological marvel have attempted to extract fundamental building blocks from the natural world in order to build tools with which to shape that world. Of course humans are not the only animals capable of making tools from the surrounding environment. That behavior has been observed even in crows (with that in mind I suggest we all be nicer to the crows; if Hitchcock's The Birds is going to happen, the crows will certainly be the organizers, and they might have cleverer plans than just poking our eyes out). But because of that particularly adept and curious brain, humans throughout history have delved ever deeper into what the fundamental building blocks of nature are, along the way developing new techniques and altogether new concepts for tools.

Corrosion is one of the most underestimated and often misunderstood forces humans deal with on a daily basis. A large part of that underestimation is the image in many people's minds of what corrosion is.  We tend to think and talk about corrosion similar to erosion: it's a geological time-scale force with which humans not only needn't engage but indeed shouldn't even concern ourselves, as it would be a futile waste of time and energy. Such a submissive attitude toward the natural forces may serve as a satisfactory spiritual practice, but to the discerning member of any competitive economic system, it is simply untenable. While the idea of battling corrosion may then conjure an image of poor Sisyphus and his infinite boulder displacement task, corrosion control can be done effectively and without anguish, as we've seen in our series of posts on the subject. Of course images and possibilities are interesting, but only hard data will tell the real story.

This is fourth in a series on corrosion control; find the previous posts here.

Within the world of corrosion control, coatings can include a number of different materials and processes, from paints to plating, to enamel and even bio films. Functionally, however, corrosion control coatings are not so different; they mainly serve one or both of two purposes: physical barrier and sacrificial anode. In order to function as a physical barrier, a material must simply prevent the chemicals which cause corrosion, i.e. water, and oxidizers like oxygen, chlorides or sulfur compounds, from touching the metal being protected. We'll see in a moment how difficult this can be.

Under seven feet of stone, in the foundation of Phoebe Hearst Memorial Hall, lies a small pool-sized room filled with all of humanity's knowledge prior to 1940.  The room is sealed shut with a welded stainless steel door which is not to be opened until 8113 A.D.  This room is the Crypt of Civilization.

This article is third in a series on Corrosion Control. Read the original over-view here and the post on cathodic protection here.

Impressed current cathodic protection (ICCP) uses the principle of cathodic protection to protect large metal objects in corrosive situations like ships or underground tanks.  As a quick reminder from the second article in this series, cathodic protection uses the galvanic reaction as a benefit to protect smaller metals items.  ICCP is used when the items needing protection are especially large or when fine-tuned control of the galvanic reaction is needed, as can be the case with ships which enter waters of varying salinity.

This piece is second in a series of posts on corrosion control.  The first post provided an introduction to corrosion control and gave an overview of some of the methods used.  Here, we are going to dive deeper into the world of cathodic protection, one of the more practiced and effective ways of controlling corrosion in process.  In a later post, we'll see how the principle of cathodic protection can be used in complex impressed current cathodic protection (ICCP) systems for delicate control over corrosion.  First, we need some background to understand how it all works.