Anti-Fouling Subsea Markings: Then and Now

Subsea signage, subsea markings, underwater identification…name them what you wish, but when it comes to it, signage is as important to subsea safety as common road signs are to motorists.

There can be numerous tree’s, manifolds and supporting hardware underneath one single oil platform: how can each template be identified?

Keeping tags on equipment, what direction its facing and if, for example, a valve is open or closed, are the main needs for subsea signage. At AQUASIGN we refer to these markings as:

  1.        2.             3.Valve markers
  1. ORIENTATION: North, South, East, West
  2. IDENTIFICATION: the name of the structure and its supporting equipment
  3. POSITIONING: open or closed

Traditional signage for the above is readily available from many outlets, but is the signage suitable for subsea use?

Just like road signs being exposed to the weather elements, subsea signage also must be compatible with its surroundings. Harsh salt laden waters with marine life is where equipment is housed, but what kind of issues do these waters bring?

  • Offshore equipment provides an attractive surface for all types of marine life to set up camp: this is called biological fouling and can impede the visibility of underwater signs – find out more in our Biofouling blog.


  • Subsea equipment is exposed to extreme pressures: these pressures push the limits of the equipment’s corrosion resistance and sealing integrity, meaning that subsea signage needs to be equally as resistant.

Regular signage will also not survive the harsh temperatures, pressures and impacts of marine life which it will be exposed to throughout the lifespan of a project, which can last up to 50 years. So, what solutions are out there for oilfield companies to use to identify their assets subsea?

Through the years there have been many solutions proposed as the answer to long lasting, anti-fouling subsea signage, let’s take a look back:

  1. Traditional Biocidal Paint

Anti-fouling paints in conjunction with stencils could be used to provide markings on subsea installations. The biocide chemical in the paint releases at an exponential rate thus giving it a relatively short anti-fouling lifespan.

The biocide used in the paint gets its anti-fouling ability from killing off organisms, not preventing them from attaching to its surface. The paint was and is still frowned upon for its environmentally irresponsible properties, leading the innovation for another type of paint.

  1. Silicone Paint

Silicone paints prevent bio-fouling by means of a foul-release system that relies on a non-stick principle to minimise marine growth. These systems are designed for coating the hulls of vessels with a speed of at least 15 knots and present an environmentally friendly alternative to biocidal systems, which is effective in reducing weight and drag.

Silicone paint systems tend to have fairly low damage tolerance. Hard fouling organisms will take advantage of damaged areas further obscuring the area of the structure requiring identification.

  1. Cupro-Nickel Markers

Copper based markers prevent fouling by the formation of a bio-fouling resistant ‘cuprous oxide’ film, which is environmentally harmful. The cuprous  oxide released when copper is in the water acts in the same way as biocidal paint. Seamark® were marker leaders in the subsea marker industry and used a copper mesh in their subsea marker design over 20 years ago.

The Seamark® technology comprised of a 90/10 cupro-nickel alloy glass reinforced polyester composite. Seamark® was a great solution until the mid 90’s, but this was outweighed by concerns on its environmental impact. AQUASIGN withdrew it from the marketplace to focus on more environmentally friendly alternatives.

  1. Flame-Cutting

Flame cutting: a process known by many names such as Oxy Acetylene Cutting, Oxy Fuel Gas Cutting, Oxygen Burning and Steel Burning. Flame cut would then be coated using either of the previous paint options described which don’t have the environmental or anti-fouling guarantee long term.  In addition, fouling may grow in between the characters of a metal sign, making it much harder to read.

Further to this, there may be no distinctive colour contrast between the background metal plate and text, which is a recognised industry standard for subsea identification.

  1. Plastic Plates  

Plastics such as Traffolyte proved only to be suitable for very short-term use. With no anti-fouling capabilities, signage was not only unreadable, but also unrecognisable after periods as short as three months.

Again, like metal plates, plastic signage was linked to an underestimation of the fouling that can occur underwater.  These plates are mainly used for temporary projects, or only topside.

So what solution does work to withstand the conditions subsea?

  1. Aquasign: Oil-exuding Subsea Markers

Pushing paint, copper, plastic and metal aside, Aquasign® – our flagship product – is a non-toxic, environmentally friendly, anti-fouling marking system which lasts 60 years.

Aquasign®, our unique oil-exuding silicone markers, were invented by Shell Chemicals Limited at their Thornton Research Centre in Chester. Shell quickly noticed that nothing seemed to stick to fish skin – why not replicate what technology is already underwater rather than bring in something unfamiliar? Minus the scales of course…  

Aquasign’s® unique surface properties are integral to its anti-fouling performance: the surface chemistry provides a hydrophobic surface that can prevent settlement at the lowest level of fouling. Additionally, our smart silicone marker secretes an oil which slowly exudes to the surface constantly renewing it, and enhancing the non-fouling properties for up to 60 years.

The first version of Aquasign® was sold in in 1985 and AQUASIGN Ltd, a standalone thought leader in the design and manufacture of subsea marking systems, have continued to develop the specification and manufacturing processes to fulfill the demands of the oil and gas industry. A lot of our improvements have come from working with global clients across 800 projects.

Subsea signage has come a long way over the years. With biocidal paint being used in the early years, it’s hard to imagine what impact this would have had to marine life, after all, 94% of life on earth is aquatic. As for copper…it can stay out of the water and concentrate on its compatibility with electricity.

Oil releasing silicone signs provide an environmentally friendly and more reliable solution for subsea asset identification. The added bonus of Aquasigns® 60-year lifespan means that time, money and resources can all be reduced by using a marker system that is fit for purpose.

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