Coating Applications in Preventing Corrosion in Water Pipelines

Out of all the scary things happening around the world these past few years, nothing scares me more than the very simple fact that water crisis have been popping up all over the world. Most of the crises have been centered in India thanks to their gigantic population, inadequate infrastructure and blistering climate. However, even more developed and relatively stabler nations like Australia haven't remained completely safe with some region down under suffering from a lack of water under record heat.

These examples of water crisis was made much worse thanks to the weather but one water crisis in particular is fully man-made, which somehow makes it even crazier and it happened in one of the world's most advance nations. The Flint water crisis, which started in 2014, was not because of a lack of water, but because the existing water "smelled terrible, tasted like metal and seemed to give them skin rashes" because of corrosion on the pipes. Flint's water crisis is a prime example on the dangers of corrosion in water pipelines, which is going to be the focus in this discussion.

It's always a bit of a catch-22 when it comes to the transportation of water. 21st century living is almost impossible without modern plumbing and for long distance transportation of water; pipelines remain the most effective method. And yet, water is also an essential part in starting a corrosion process, which would eventually degrade the pipe so much that the corrosion began to seep into the water if not properly anticipated just like what happened in Flint. What makes it worse is that when pipelines are used to transport drinking water, they're typically treated with chemicals that would make corrosion even worse.

While we know water as mostly H2O, water can contain several other chemicals that could have an impact on the corrosion process. Treated water might contain CaCO3, which could cause the formation of scales along the pipe's inner surface. These scales actually help minimize corrosion by preventing the water from coming into contact directly with the pipes but when left unchecked would eventually clog the pipes. If the water in question has a higher pH level compared to tap water, alkaline water for example, the pipes might be under the risk of microbiologically induced corrosion because of the microorganisms contained in the water.

As has been hinted at when I first mentioned Flint, corrosion in pipelines are dangerous not necessarily because they can compromise the structural integrity of the pipelines but because the corrosion could infect the water with some serious health considerations. We might be able to live with slight discolorations and a downgrade in odor and taste but skin rashes is definitely not something you want to deal with, hence the importance of coating. In water pipeline applications, it's not enough to make sure that the thickness level of the coating is within the recommended level using paint thickness gauge, it's also important to make sure that the coating pose no serious health considerations to the water.

Polyurea remains one of the most popular coating choices for water pipes because of their corrosion resistance and chemical resistance. As such, they are capable of preventing corrosion even from heavily treated water and additionally, polyurea bonds particularly well to ferrous metals, guaranteeing excellent adhesion and long-term durability. The downside is that the initial cost in polyuera coating application would be rather high as they're pretty expensive and requires a comprehensive surface preparation process.

Another popular choice is the use of FBE coatings which in addition to their excellent corrosion resistance is that FBE has superior erosion resistance as well which helps a lot as water pipelines would have to deal with moving water almost 24/7. FBE coating comes in powder form and they're applied first to the cleaned pipes before being cured at a temperature of around 200 C. As typical with powder coating, this curing method has excellent adhesion at the downside of a relatively complicated application process. This makes for excellent durability at the cost of a tricky maintenance process.

As with FBE coatings, polyurethane coatings also boast a superior erosion resistance in addition to their corrosion resistance. What's remarkable about polyurethane is that they are capable of achieving such superior mechanical properties even with a low coating thickness level, making it possible to achieve a high flow rate and efficiency even with the addition of a protective coating. Because of their short curing time however, polyurethane can be somewhat tricky to apply, usually needing the help of an expert just for the application process.

A highly economical alternative for water pipelines is the use of cement mortar which provides reliable protection for water pipes. However, cement is not suitable for water with high chlorination of for a pipeline system in which the traveling speed of the water regularly exceeds 6 meters per second as that could seriously damage the concrete. However, the use of cement lining needs to be carefully monitored as it is very much in the realm of possibility that trace contaminants could leach into the water.