The way we preserve our assets is costing us millions

The way we preserve tanks, pipes, valves and machines is 30 years behind the times.

In polite language: “Too many marine assets are prematurely deteriorating, due to inadequate attention to modern preservation practices.”
– Or in plain language: “To many ships and rigs are needlessly rotting away due to ignorance of new preservation technologies.”

For some reason, the extreme usefulness of modern corrosion inhibitor technologies are still not well understood in oil and gas circles.

In 2010, we delivered two of the newest cyber jackups to an offshore contractor. The rig manager told me last week that the five year surveys revealed that every valve in the C&K (choke and kill) manifolds had internal corrosion, bad enough, that all the valves needed remachining, at a total cost nearly that of buying an entire new manifold.

Had we been aware of how to use Volatile Corrosion Inhibitors (VCIs) back in 2010, we could have kept both manifolds in near new condition, at an enormous cost saving to the owner.
Asset preservation is not rocket science; the world’s militaries have
already figured out how keep even cold stored equipment in near-instant combat readiness. Vendors whose products are used to cold preserve military equipment in ready-to-use condition are more than happy to share their skills with the offshore industry.

Traditional methods of preservation are clunky, expensive and hard to use. For example to guarantee that ballast tanks would not corrode, the only way used to be grit blast, followed by a two part mix multi coat paint system.

Today, we can stop corrosion inside tanks and cooling systems with cheap and simple VCI inhibitors.

The name of these inhibitors, VCI, gives a hint how they work: all are chemicals which give off a protective vapour, which forms a super thin protective film deposit on vulnerable surfaces. Anybody responsible for managing oil and gas equipment should know what the ten basic types of VCIs and how to use them, in what application. This article is not a user manual (there is plenty of information on the internet) but rather a starting point of what to think about.

VCIs are relatively easy to apply and if you properly seal the protected item, they can preserve sensitive systems for years.

The latest family of VCI compounds, developed over the past 30 years, have low toxicity, similar to that of table salt (2,000 to 3,000-mg/kg oral LD-50). Their vapours protect against corrosion in the presence of water vapor, chlorides, hydrogen sulfide (H2S), sulfur dioxide (SO2) and nitrogen oxides.


In managing marine assets, there is still a lot of ignorance about the most basic topic of preserving steel. Here is a quick overview of what marine asset owners and managers should know.

The best way to protect steel ballast tanks, spud cans and piping from sea water corrosion is still the old fashioned methods of blasting and painting, but such methods are expensive, time consuming and not always viable. Today’s amine carboxylate based inhibitors greatly reduce corrosion in any steel container that holds water e.g. cooling systems, spud cans, deluge piping, engine radiators, ballast tanks.

In the case of closed cooling systems, the post WW2 period used a very effective class of chomate based inhibitors. But they were banned in the 60s due to their toxicity. Chromate inhibitors (typically yellow) were replaced by inferior nitrite based inhibitors (typically pink) which needed a high level of skill and attention to be effective. Then about 20 years ago, today’s new class of vastly superior carboxylate based inhibitors very slowly started to appear. Fifteen years ago, Caterpillar became one of the first to offer long life carboxylate based “ELC – Extended Life Coolants” (while still offerring nitrite based coolant chemicals as standard).

The mechanism of amino-carboxylate based vapor-phase corrosion inhibitors prevents corrosion of metals in three phases: within the solution, at the water line, and above the water line. VCI-based compounds prevent corrosion in the areas which are not reachable with other corrosion inhibitors. They are vastly superior to anything previously used. So it is a surprise how many owners still use obsolete nitrite inhibitors, probably out of habit and unawareness.
The new carboxylates can be used not only in cooling systems but in pipework and ballast tanks as well.

Carboxylates are long lasting (measured in years between treatment), safe, easy to use and well worth the money considering the protection they afford. (If not properly monitored, nitrites inhibitors can actually accelerate corrosion.)

I mention this, because it seems logical to many that fresh water is widely considered to be less corrosive than sea water. Especially in steel spaces that must stay full of water, such as spud cans. This however, overlooks the issue of SRBs (Sulphate Reducing Bacteria) which can eat holes in steel even faster than salt corrosion. An SRB is organic matter (bacteria) which respirates without oxygen. Some SRBs can breed more prolifically in fresh water than seawater; SRBs give off highly corrosive hydrogen sulphides as their waste product. If you pump some water from a spud can and it has that a stinky H2S smell, you have SRB-related corrosion occurring inside the can. If an SRB problem is identified, DON’T just dump a load of biocide into the tank or pipe as that can worsen the problem. Dead bacteria produces more H2S. The tank may need to be emptied and cleaned.
Moral: always use a biocide from Day-1.

Today’s family of carboxylate based VCI inhibitors are a big advance in reducing steel corrosion. Start with an empty tank and spudcan, to which an oil based VCI concentrate + biocide is poured into the manholes. Then fill the tank with water. The VCI inhibitor floats on top of the rising water and coats all internal surfaces. If you want to empty the tank , you can store this VCI-water mixture and use it to treat other tanks or pipes. There are various types of VCI tank treatments in the market. All do a much better job of preserving steel than any of the old ways.

CONCENTRATIONS typically vary from 1 to 5%, depending of the brand and application. Most VCI treatment chemicals come with built in anti SRB biocides.

COST: A popular brand of carboylate VCI inhibitor, such as Vappro 748 costs about USD17/liter and one liter treats a ton of water
(1,000ppm). So a large spudcan on a 350ft jackup rig which contains about 400 tons of water, will cost 400 [times] USD17= USD7,000 worth of chemical. Ballast tanks, which can be left empty, work out cheaper, as the same batch of VCI treated water can be pumped from tank to tank. Get the VCI vendors to suggest different solutions.

Cortec’s M-645 is an oily VCI product for tanks. It floats on top of water, so an entire tank can be protected simply by adding the correct amount of product. Fill the tank with water, then empty it again. This leaves an oily VCI film on the tank’s internal surfaces, claimed to be good for years, (so long as VCI vapour status is regularly monitored).

The VCI vendors sell useful electronic “sniffers” and test kits that can detect whether additional vapour producing chemicals need to be added.

4 comments to The way we preserve our assets is costing us millions

  • In the interests of better educating those who manage marine assets, should we be publicizing the availability of familiarization courses in the latest techniques of marine preservation?

  • Jim Gelpi

    A timely and interesting blog as I am currently looking into providing guidelines re: long-term storage of ROV Systems.

  • A note to the author, the correct spelling is Cortec not Coretec.

    Cortec’s VpCI’s are often environmentally friendly with discharge approvals to ocean, also typically for oil systems the inhibitor added is compatible with the system and can be left in during operation also. Increasing speed and readiness of equipment.

    • evanjbatam

      Hi Philip

      Thanks for your correction. I have written twice to your Vice President Sales in change of Process / Water Treatment / Mothballing / Lay-up / Powder / Power Generation requesting we do an interview on how your products can be used in Mothballing and Lay-up but he has been too busy to even bother to reply.

      We are currently being advised by some other VCI vendors who at least provide some knowledgeable and helpful advise.

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