‘The most durable protection for underground storage tanks.’

Corrosion control at underground storage tanks is an important issue. Effective leak protection at underground hydrocarbon “holders” not only protects the infrastructure from decay but also the underground water layers from contamination. The East Flanders-based Cathec has a method for this that looks beyond, and is more sustainable than, the traditional approach.

Underground storage tanks have their advantages – they are not in the way and save space – but they also bring difficulties: they are subject to wear and tear, and that damage can lead to leaks. In the event of a fuel leak, as a petrol station operator you are looking at huge costs and damages. And so it is extremely important to keep storage tanks in good condition, says Sam Weydts of Cathec. “A small defect can cause major problems, because one litre of leaked petrol or diesel can contaminate up to a million litres of groundwater.”

The way to completely stop the corrosion process is electrochemical technology, cathodic protection. In its simplest form, this is done through ‘sacrificial anodes’, explains the Cathec founder. “Then, using a wire, some anodes are attached to underground tanks via an above-ground measurement point. The anodes “sacrifice” themselves for the benefit of the storage tank by sending its energy through the soil to the tank.

At petrol stations, there is a liquid-proof covering of asphalt, concrete or bricks above the storage tanks. All fine, people think, but what they forget is that those sacrificial anodes gradually lose their power, like a battery that slowly drains. After ten years, your protection has become a lot less adequate or worse, completely gone. If you want to intervene then, you have to open up the slope above.”

Optimal protection

This can be done better, more conveniently, and cheaper in the long run, Weydts thought, and he founded Cathec. Johan Van Hemelryck, who has 25 years of experience in this sector came on board at Cathec this year and shares his extensive expertise and practical experience in the field of cathodic protection.

The current-pressure system developed by Cathec (called ICCP or Impressed Current Cathodic Protection in the jargon) stops corrosion completely in a sustainable way. Current pressure systems are ideal for new tank installations and are the solution for non-functioning older systems with sacrificial anodes. “To install our system, you don’t even have to open up the liquid-proof surfaces,” says Weydts. “We drill a small opening, at an appropriate distance from the storage tank, install some anodes, and connect them to the storage tanks via an adjustable current source. Because you can adjust the protective current, which is not possible with sacrificial anodes, you can ensure optimal corrosion protection at all times. Often, control of the entire system can even be automatic. For this, a reference electrode is set up near the tank wall and the current situation in the soil is monitored (e.g. dry or wet subsoil, stray currents) and, based on this, the protection is adjusted if necessary.

Stray currents

And protection is needed, Johan Van Hemelryck stresses. “Whether corrosion protection should be installed used to be determined in very many cases, especially in Wallonia, with a soil corrosion measurement prior to the installation of storage tanks. Many of the new tanks were installed between 1995 and 2010. However, people forget that environmental conditions can change a lot in that time. Some examples: a tank station next to a recently electrified railway line, the construction of a high-voltage power line nearby, road works that caused vibrations in the soil and consequently cracks in the coating. Especially for the gas stations where it was not considered necessary to install cathodic protection at the time, and where we do not know the underground condition, the condition of the tank wall is a big question mark.”

“After all,” adds Weydts, “there can be ‘stray currents’ in the subsurface due to pipelines nearby being cathodically protected, for example. The busier it gets in the underground like this, the more there is a need for cathodic protection.”

“Many tanks also date from the beginning of this century, so they have been underground for about twenty-five years,” Van Hemelryck continues. “So their protection could do with an upgrade, because the anodes that were installed there when they were placed are getting close to the end of their life after a quarter of a century of service by now. That is one of the things we evaluate when we carry out maintenance checks at filling stations: the amount of power that is effectively still supplied to their storage tank.”

Cheaper in the long term

Cathec takes care of the entire process of cathodic protection, from installation to service afterwards. “Anodes, cabling, measuring poles, power sources, measurements, test report in accordance with the prevailing web and standards,…. We do it all,” says Weydts. “Incidentally, before we proceed with installation, we always come to carry out an on-site expertise, so that we know what is needed for the customer to be served optimally. We do this with appropriately trained personnel holding AMPP (formerly NACE) certifications”

An ICCP approach like Cathec’s really does last a long time, Weydts and Van Hemelryck stress. “The minimum lifespan is proven in practice to be 20 years,” says the former. “That way, what may at first seem like a big installation cost is still a lot cheaper than if you have to have a new sacrificial anodes installed after a few years.”

Curious about Cathec’s capabilities? Call +32 9 218 19 67 or email info@cathec.be