The impact of sea water on the new Sea King helicopters Print
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Helikopter_SeakingA classic morning ritual of mine: doing windmills with my arms in order to get my sore limbs up and running at full speed. Having breakfast while listening to the radio. The first headline blasting at me through the speakers: “The helicopters which are supposed to replace the Sea King, already seem to be affected by sea water”. Talk about windmills… The problem is supposedly already known to Dutch and French forces, and people are concerned that the Belgian helicopters will be suffering the same fate. Is that concern justified?

So, what does sea water actually do to structures that are exposed to it? Honestly, not much good. Sea water is a highly corrosive substance and therefore, many engineers are working hard every day to develop and optimize new methods meant to protect materials used in, on, at, and above the sea from corroding. The main culprits are (among others) the chlorides in the sea water, and more broadly, all of the so-called halogens. Other products contained in sea water can also have a negative impact, such as sulfates, phosphates and certain microbiological organisms. If these products are able to attach themselves to metal structures along with the sea water, they could provoke a process called pitting corrosion. If the sea water manages to affect cracks and crevices, crevice corrosion could occur. When stainless steel parts are exposed to water that contains chlorides at high temperatures, you might get stress corrosion, etc.

“High temperatures in a helicopter?” Sure, near the motors or when bearing systems start to heat up, the temperature of these parts can rise a couple of dozen degrees in a very short period of time. Of course cooling systems are in place where needed, but if those systems somehow lack power, if they aren’t positioned correctly or if there’s something wrong with their controls, problems can be right around the corner. Cracks and crevices can be found everywhere on a helicopter. What’s more: a helicopter is constantly exposed to massive vibrations, and if just one bolt is improperly tightened, it will quickly loosen and lead to crevice corrosion.

We haven’t even discussed the layers of paint yet. Their quality depends on a multitude of different factors. The first is the type of painting system that was chosen – primer, intermediate layers, surface layer; just as important are the quality of the paint itself, the quality of the pretreatment of the paint surface, the application method, ensuring that the previous layer has dried properly before applying the next layer, etc.

helikopter_NH90As you can see, a helicopter is a complicated piece of machinery that is threatened by many types of corrosion risks, just like your heating system and your car are exposed to a lot of corrosive attacks. And yet people still underestimate the importance of protection against said corrosion. Not enough attention is paid to regular inspection and a follow-up of structures which are sensitive to corrosion. The steel reinforcement of the “boekentoren” (book tower) in Ghent (2003), the lighting poles along the E19 highway (2011), the steel support structure of the “boerentoren” (farmers’ tower) in Antwerp (2014) and now the new NH-90 helicopters. Stopping corrosion is a Utopian dream, but it’s about time the prevention of corrosion got a little bit of attention.

Take this tip to heart: by the time you start seeing ‘rust’, it’s already too late. Rust is not the same as corrosion, but rather a consequence of it. Want to know more? Our previous blog post will tell you all about it.