Advanced Marine Coatings

Long term bio-fouling control trials continue to show encouraging results with different coatings

Robert van Merkestein \ October 27, 2021

Marine biofouling is the natural accumulation of microorganisms, plants, algae or small animals on submerged or wet surfaces. Left unchecked, biofouling increases hull surface roughness, fuel consumption and greenhouse gas emissions.

Increased roughness presented by a heavily fouled ship hull can result in powering penalties of up to 86% at cruising speed; even relatively light fouling by diatom ‘slimes’ can generate a 10–16% penalty. Without effective antifouling (AF) measures, vessel performance, fuel consumption (and therefore greenhouse gas emissions) are negatively affected.

Bio-fouled vessel hulls from around the world can introduce non-indigenous marine organisms which may contaminate marine waters and compete with native species.

It is estimated that 75% of introduced marine species have established in Australian waters as a result of biofouling on marine vessels.

Owners of marine vessels spend considerable time and money to mitigate the effects of fouling on vessel performance and biosecurity.

The challenge

Anti-foul paints and coatings provide protection against corrosion and contain biocides that slow bio-fouling.

The toxicity of these biocides and their negative effect on the marine environment is well documented.

Anti-fouling agents such as tributyltin oxide (TBT) have been historically used on ships and recreational boats to prevent biofouling. TBT slowly leaches out of coatings into the marine environment where it is highly toxic toward non-target organisms. After it led to the collapse of local populations of organisms, TBT was effectively banned globally.

Today, although the biocides used are less toxic there is still growing concern that they can also contaminate and damage marine eco-systems.

Further, the cost of anti-foul coating application and maintenance can be very high.

“Typical costs of hull treatment during a drydocking can range from thousands to several million dollars depending on vessel size and the type of coating system applied”

Rob Van Merkestein
Business Manager – Bioactive Materials

 

“Marine biofouling control is similar in many ways to pest and disease control in agriculture – both rely on toxic or biocidal chemicals and both are under regulatory pressure. The marine coating program aims to develop non-toxic bioactive additives that improve the effectiveness and durability of antifoul coatings to meet operational and environmental requirements. Results from our initial studies in Australia indicate our materials are compatible with common formulations and their inclusion coincides with significantly reduced biofouling. This, and the interest by coating manufacturers undertaking their own studies at various locations around world, is very encouraging.”


References:

Trends in the development of environmentally friendly fouling-resistant marine coatings, James A. Callow & Maureen E. Callow, 2011
Biofouling and its Implications on Marine Health, Boat Safety and Australia’s Biosecurity, OceanTimeMarine, 2017
Understanding marine biofouling: How anti-fouling systems prevent growth, by SAFETY4SEA, 2018.
Advances in marine antifouling coatings and technologies, by Claire Hellio and Diego Yebra, 2009.

A solution?

A 26-month study assessing the effect of the addition of Calix bioactive material to an in-market commercial anti-foul paint formulation has been completed.

The submerged exposure study was undertaken in the tropical waters of northern Queensland.

The addition of Calix very high surface area (“bio-active”) magnesium oxide (MgO) (200 g/L) to an in-market aluminium compatible anti-foul paint coincided with a significant and consistent increase in clear, essentially un-fouled area.

Ablative; copper thiocyanate & zinc pyridimethione -effect of MgO doping, 26 months exposure


MgO addition coincided with 88% less fouled area when compared to the in-market paint formulation as well as a substantial reduction in the amount of other fouling organisms including highly problematic barnacles.

 

Images of anti-foul painted panels after 9 months submerged exposure.

 

Ablative marine coating – no additive


 

Ablative marine coating – 200 g /L Calix “bio-active” MgO

Calix’s Biotech line of business

focusses on developing novel, safe “bio-active” materials for multiple applications

 

Calix’s Biotech materials are based on magnesium minerals and derivatives.

Our approach:

Proof of concept → R&D, External engagement &
Co-development → Tech. licencing → Manufacturing

Why are Calix’s materials exciting?

Calix’s Biotech materials are based on magnesium minerals and derivatives.

Magnesium oxide and hydroxide are intrinsically safe to us, and the environment.

  • Our materials are non-toxic.

We fine grind natural magnesium minerals to produce particles around the size of plain flour and then heat this to produce bioactive MgO powder.

  • Our materials are bioactive. Bioactive: having an effect on a living organism.

Source: https://www.merriam-webster.com/dictionary/ bioactive

Source of bioactivity

Oxygen reacts on the surface of our materials to produce reactive oxygen or ROS.

ROS is a key component of many immune system responses – it’s a necessary and natural part of life.

Humans, animals and plant immune systems produce ROS to fight-off infection. ROS inhibits the growth of many pathogenic microorganisms, including it seems, biofouling marine organisms.

Calix’s BIOME (BIOactive Material Engineering) program aims to exploit our core technology and the unique physical and bioactive material properties to develop safe and sustainable materials to address global challenges. ‘


 

‘Mineral Honeycomb’– a close-up of our unique, highly porous and active magnesium oxide

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