What is Corrosion?
Written by: Brian Pottebaum, Director of Training Services
What is corrosion?
Corrosion is the gradual degradation of a material by chemical reaction with its environment, most commonly occurring with metals. A good example of this could be a rusty old nail that you find on the ground. Over time, the shiny steel nail gives way to corrosion, or in this case “rust”, because it was exposed to moisture and weathering.
However, corrosion can also include non-metallic materials such as plastic, fiberglass, rubber and many more. An example of this could be the weather checking or cracking that you find on an old tire. When rubber tires are exposed extensively to sunlight, precipitation, chemicals, and seasonal temperature fluctuations, the rubber becomes rigid and results in cracks in the sidewalls and the tread grooves.
In the petroleum storage tank industry, we must also be aware of corrosion on all components regardless of the construction material.
What causes this corrosion?
Corrosion, or degradation, can result from exposing components to non-compatible liquids and compounds, bacteria, and other microorganisms (also known as MIC), as well as exposing unprotected metal to a high moisture environment. Every material has specific limitations, and you need to know what they are to prevent over-exposure.
Can corrosion be controlled?
The simple answer is yes, it can be controlled. However, corrosion in most cases cannot be stopped entirely, only slowed down or made less severe. In all cases, certain activities must take place to mitigate the corrosion and gradual breakdown of the components outside normal “wear and tear”.
Corrosion Control
Once we are aware of the risks of corrosion we can mitigate appropriately. Here are some simple suggestions:
- Check compatibility. Make sure your tank system is compatible with the fuel you intend to store and dispense, especially when switching to higher concentrations of renewable fuels. Many older systems are not approved for that application. You will need to check every component that contacts the fuel, from tank to nozzle. State and Federal regulations require fuel compatibility documentation. Your service provider can assist with this.
- Clean fuels. Fuel storage requires best management practices such as routine tank cleaning and keeping the fuel fresh. If you don’t have rapid turnover in the storage tank, additional treatments and additives may be necessary to stabilize the fuel and control microbial growth.
- Keep water out. Manage the fuel system by checking for water every month. All tank access ports must be liquid tight, including the fill cap seal. Damaged spill bucket drains are a common culprit that can let water in tanks. Most tank monitoring systems will indicate if water is accumulating in the fuel system. Another easy way to check is with a tank measuring stick and water finding paste.
- Protect metallic components. All metal components within the system must be protected from corrosion, especially if they are buried. This is either done by isolation (coating, lining, painting) or by adding cathodic protection, such as galvanic anodes or impressed current. Those systems require testing and recertification every three years. Impressed current also requires period rectifier checks. Your service provider can help you with this as well.
Exercise routine maintenance and proper care so the fuel system will not suffer accelerated corrosion. While nothing lasts forever, we can take proper steps to keep the system working properly as it was designed.