New corrosion prevention strategies are constantly being developed, tested and moved into production, yet the need for robust corrosion control programs is as widespread as ever. Metallic corrosion impacts nearly every U.S. industry, with manufacturing and construction bearing most of the burden due to their heavy reliance on carbon steel.
According to The American Galvanizer's Association, carbon steel amounts to around 85 percent of all steel production. And while this alloy is undoubtedly one of the sturdiest building materials available, it is still quite susceptible to natural processes like oxidation. Over time, localized environmental forces eat away at the carbon steel's surface, weakening the integrity of the structure it belongs to. These (usually atmospheric) forces include metrics like moisture, temperature, humidity, rainfall, levels of pollution and air salinity.
How quickly does carbon steel corrode?
Since no two locations are exactly the same, it's difficult to calculate a uniform corrosion rate for carbon steel that can accurately reflect real-world conditions. The AGA lists the following corrosion rate estimates based on different atmospheric environments:
- Rural areas – 4 to 60 micrometres per year
- Urban areas – 30 to 70 micrometres per year
- Industrial areas – 40 to 160 micrometres per year
- Marine areas – 60 to 170 micrometres per year
Marine environments seem to have the highest corrosive potential when compared to other locales, depending on the water's specific oxygen content, temperature, chloride levels and much more. This just goes to show that a one-size-fits-all solution to metallic corrosion in very unlikely, as a comprehensive prevention plan will inevitably rely on a deep understanding of the environmental factors at play.
Essential oil extracts as corrosion inhibitors
Research into corrosion inhibition has taken an interesting turn over the past few years, as a growing number of experts have begun experimenting with "green" chemical compounds. An early January article from Science Trends reported on the effectiveness of several new essential oil extracts for reducing carbon steel corrosion. The article claims that inhibitors made from condensed hydrophobic fluids and volatile aroma components may soon replace traditional chemical compounds in the corrosion protection market.
Inhibitors are typically developed using both organic and inorganic ingredients, which work together to form a protective film on carbon steels that "suppress the transfer, diffusion, and electrolytic transport of corrosive anions responsible for redox electrochemical reactions and surface degradation," according to a recent research paper published in Results in Physics. The paper argues that a vast majority of commercially available corrosion inhibitors are unsustainable, citing high toxicity, strict regulations and extensive costs as limiting factors.
At present, researchers are quite optimistic about the use of rosmarinus officinalis (rosemary) and trypsin (enzymes found in most vertebrates' digestive system), though the compounds' performance is heavily reliant on high concentrations. Corrosion experts will need to aggressively test the compounds in environments that replicate real-world conditions before these "organic" inhibitors can be commercially deployed. But nonetheless, this breakthrough stands as yet another example of how rigorous corrosion testing can drive innovation and discovery.