Antifoul Paint

Antifoul Paint – Tips, reviews, research and application          by Simon Phillips Seaway Yacht Delivery

The many different types of antifoul paint on the market sometimes make for a tricky choice for the boat owner. Choosing the right type of paint depends mainly upon what type of boat you have, how often you use it and the location of where she is kept.

After applying different paints on different vessels in different locations, I have compiled a report on the findings. Locations include around the UK and in the Mediterranean.


The different types of antifoul paint can be classified into 5 main sections;


Hard Paint

Soft Paint


Silicon based paint

Self Polishing Paints


Choosing the correct type of antifoul paint can be difficult, the question of where am I going cruising, how fast is my boat and how often am I going to be using her. These are all important considerations to be taken into account when deciding the paint type.

The majority of antifoul paint companies use a similar combination of biocides for the prevention of marine growth. The differences come in how the structure of the paint releases the biocides and the colour pigmentation. There is a more environmentally friendly product available, which is the Silicon paint. The biocide will leach out of the surface paint over time, which results in marine growth on that inert surface. Removing this layer of paint either physically or chemically will present a new layer of the biocide laden paint.

For example; a motor yacht capable of 30 knots or more you need to use a hard antifoul paint. Hard antifoul paint works by the friction of the water removing the marine growth along with eroding the surface of the paint. However, unless you are doing this sort of speed, and frequently – most weekends, then you would be advised to use a softer type paint, as should be used on cruising sailing yachts.

 Soft Rosin based eroding paint 

This paint type has a soft soluble binder that gradually dissolves in water leaving a fresh layer of paint and biocide. Generally, it is better to put on two or more coast of this paint on your boat as this works by dissolving! The thickness of the paint gradually reduces until it eventually disappears altogether. This is suited to sailing yachts and displacement motor boats due to their relatively slow speeds. This paint will wear out quickly if applied to a fast planning boat that is regularly driven at speeds of 30 knots or more.

Self-Polishing paints

The self-polishing paint works in a very similar way to the self-eroding paint. However, here is used a mix of soluble and insoluble glues that require at least a tidal flow of water passing across the paint to wear it down, revealing the fresh layer beneath. This type of paint will not go off if the boat is out of the water. Stronger binding agents enable this type of paint to be on fast boats provided they don’t regularly exceed 25 knots.

CoPolymer Type Paint

CoPolymer paint replaced the tin based TBT paint that was banned in the 1990s. (Although this did work very well!!).   It was discovered by goodness knows who, that it caused some microorganisms to change sex! Unlike the aforementioned paints, the acrylic binder reacts to salt in the water, thus continuously exposing a fresh layer of biocide laden paint. This means that it is not reliant on any movement of water and works regardless of whether the boat is lying idle in the marina or cruising regularly.

Hard antifoul paint

Hard paint is mostly used on fast planning sailing yachts and fast motor yachts as it will not erode at high speeds. As the season unfolds, the biocides leach out and it gradually becomes less effective. If the boat is removed from the water after launch, it can also form an impermeable layer which prevents any further biocide from leaching out even when launched again. This also means that the boat is more prone to paint build up over the years which may need removing at some point to prevent it cracking and peeling.

Silicon paints

Rather than using biocide chemicals to stop growth, this paint forms a highly slippery surface which  prevents marine growth from getting a grip on the surface. Some growth will still appear when left unused in the marina but as soon as the boat moves at around 8 knots any significant growth should wash off. The manufacturers also claim to reduce friction in the water, increasing efficiency and speed. The benefits of this type of paint, mean that  it must be applied  to a properly prepared gel coat surface. This can be an enormous task of removing all the old antifoul to expose the gel coat. This type of paint cannot be painted over if you choose to revert back to the non silicon type antifoul. It must first be removed.

Toxic paint and our laws.

Here in the UK, we are in between the laws of our Nordic neighbours and those of the Mediterranean.

In Nordic countries, the regulations are tight in terms of what is banned, they are tough and very much more aware of the poisons in the paint and do not wish these to be used. The Mediterranean countries have a very lax legislation for the types of paint allowed. We in the UK are somewhere between. When pressure washing also, Nordic countries only allow this in specialist sites where the run off from the pressure washing is drained and filtered before going back into the water course.

Paint legislation 

The UK is currently in the mid-way between Mediterranean and Nordic countries in terms of legislation. Mediterranean countries are far more lax in terms of what can be used, and who can do it. The story is the opposite in the Nordic area, with some paints that are available in the UK being banned. It continues with removal too, with specialist sites that wash, drain and filter all residue being mandatory when working with antifouling. While nothing is set in stone for UK shores, it’s worth noting that changes that affect us all could be just around the corner.

Testing results;

Results of testing for weed / marine growth prohibition and colour fastness.

A problem faced by choosing certain colours is that over time, they will change. I have found that paint, especially around the waterline discolours the most.

Here is a list, in order of best to worst of 10 antifoul paints from well known manufacturers’for the ability to resist marine growth and retain colour. Marks are out of 100.

Seajet 038                                          85

Hempel Silic One                              80

Aquacote                                            72

International Micron 99                  72

Hempel Hard Racing                        68

Jotun Racing SH                               68

Flag Performance Extra                    64

Hemple Mille NCT                             64

Jotun Mare Nostrum                         64

International Trilux 33                      60


It is clear to see the difference between the best and worst here. The SeaJet 038 in my opinion worked the best, closely followed by the silicon product.

Happy Antifouling!

Please feel free to ask any questions on this. Many thanks, Simon Phillips Seaway Yacht Delivery