Best antifouling protection slow steaming idle times

Best antifouling protection for slow steaming and idle times

6:25 AM, 17th February 2018
Best antifouling protection for slow steaming and idle times
Protective anti-fouling coatings prevent fouling organisms from attaching to the ship's hull during service, thereby avoiding a rise in fuel consumption and stack emissions.

By Henrik Dyrholm

Following the global financial crash in 2008 there has been a continuous uncertain economic landscape haunting most markets. Trade growth has slowed with many countries continuing to manage high levels of debt and unemployment. In general, shipping is perceived as a good measure of the global economy, so whilst tonnage continued to grow in the period following the financial crisis the decrease in cargoes combined with an oversupply of tonnage has significantly impacted freight rates.

It is, therefore, no surprise that ship owners and operators are eager to find ways to maximise the efficiency of their vessels. One way in which they do this is by investing in protective anti-fouling coatings. These coatings prevent fouling organisms from attaching to the ship’s hull during service, thereby avoiding a rise in fuel consumption and stack emissions. Fouling organisms that attach to the hull increase frictional resistance, which can affect both the performance and durability of the vessel, impacting the amount of energy required to propel the ship at a given speed.

Antifouling systems

Antifouling systems are by no means new. Some of the disadvantages of marine biofouling have been recognised and combated for more than 2,000 years. Early adopters used a vast array of solutions from copper sheathing, tar and wax, through to physical methods such as scraping biofouling off the ship’s side.

These paints, or coatings, have evolved greatly since the 1800s to the products that are currently available, and it is well known that the fuel consumption of a vessel is strongly influenced by the quality of the antifouling system used. At Hempel we have a deep-rooted history within the shipping sector; supplying trusted marine coatings for over 100 years. Significantly we launched the world’s first antifouling coating for ships’ hulls in 1917.

There are three fundamental technologies currently being used to combat fouling; antifouling paints, fouling release paints and fouling defence coatings. Antifouling paints are chemically active coatings which act on the marine organisms by inhibiting or limiting their settlement. Fouling release paints are non-chemically active coatings which prevent adhesion or reduce adhesion strength via physical means. Finally, fouling defence coatings take the best of both worlds, achieving outstanding fouling prevention properties with only a fraction of the active ingredients.

Antifouling coating solutions and their performance are dependent on several factors. First and most importantly, the types and concentrations of the active ingredients used (biocides) and the speed of surface polishing of the paint. There is industry-wide recognition that a stable polishing rate is required for an antifouling coating to perform for long periods of time - the active ingredients can be released at a constant speed thereby reaching constant surface concentrations. The higher the fouling pressure, the higher the required amount of active ingredients at the coating surface.

The concentration of fouling depends on a range of factors that include; water temperature, nutrients, light and vessel speed. For example, fouling in warm waters tends to be greater and therefore harder to protect against. In these extreme conditions, fouling is typically tackled by increasing the biocide content in the paint or by increasing the polishing rate – in both ways the total content of biocide is increased. An alternative to keeping the hull clean without increasing the overall content of biocide would be to introduce an intelligent biocide package in the formulation that combines biocides with complementary effects.

This concept is based on the fact that not all biocides have the same effectiveness against the different micro-organisms that flourish in the marine environment. This ‘smart’ biocide can therefore provide a broader biocidal range against different micro-organisms with a lower total biocide content.

At Hempel, we recently launched two antifouling coatings, Globic 9500M (M for maintenance) and 9500S (S for static), that combine the controlled polishing and controlled release properties of a premium binder system – our patented nano acrylate technology with a premium biocide package containing four different biocides. This winning combination delivers superior performance at different trading speeds and outperforms conventional self-polishing coating (SPC) technologies particularly during slow steaming and outfitting.

What is behind the technology?

Nano acrylate technology consists of a separation of active and inert monomers (molecules which form polymers) into two different acrylic polymers. These two polymers are arranged in nanometre size spheres (nano capsules), with a core and shell structure.

The core polymer consists of a highly reactive acrylate polymer containing hydrolysable groups. It is the component responsible for the self-polishing effect in the coating. The shell polymer is based on hydrophobic acrylate polymer that regulates the rate at which seawater penetrates into the core. When seawater comes into contact with the nano capsules, it penetrates the hydrophobic outer shell triggering the controlled polishing of the coating.

The new range

The new Globic range is built on this technology and delivers premium antifouling protection delivering customers a potential 2.5 per cent reduction in speed loss - equating to significant fuel savings. This in turn lowers CO2 emissions for the ship operator helping to improve the operational efficiency and miminise their environmental footprint.

Globic 9500M is designed to protect against slime as well as soft and hard fouling in all conditions. Globic 9500S is designed to protect against hard-fouling even during extended outfitting periods. Together these two coatings deliver unparalleled anti-fouling protection offering improved operational efficiency, flexibility and a high return on investment. Additionally, the patented microfibres incorporated in the paint give Globic 9500M and Globic 9500S a best in class mechanical strength to avoid cracking and peeling.

In a period of global financial uncertainty and volatility, the level of efficiency that a ship or fleet can perform at is of paramount importance. At Hempel, we will continuously endeavour to match the needs of our customers, by providing solutions which adapt and evolve to the challenges posed by an ever-changing world. 

Author: Henrik Dyrholm is Global Product Manager at Hempel A/S.

© Chemical Today Magazine


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