Choose your antifouling

What is antifouling?
Antifouling is protective underwater paint developed to release toxins (biocides) to slow down development of fouling (algae, shellfish,…) on the hull. To achieve it, antifouling job must be renewed every year to remain effective.

Why using antifouling?
Why using antifouling on a hull (underwater area) : It protects the substrate/surface and avoids colonization of fouling on the hull and resulting consequences (Roughness increases resistance through the water -> causing lower speeds -> consuming more fuel).

Which are different types of antifouling?
Self-polishing antifouling :
This type of antifouling contains partially a resin of active substances (biocides) which repels/discourages fouling.

Once in water, the paint film wears out because of water friction on the hull and the resin breaks down in a controlled way, continually exposing fresh biocide layers. This gives constant performance throughout the season, very smooth finishing to the hull (recommended for boat owners looking for the best glide.), and reduces build-up of old antifouling.But self-polishing effect may cause problem in some situations : for boats mooring in marina with stagnant water, or with long non-sailing period, or sailing in areas with a strong current, or for speed motor-boats (above 25 knots).
Hard matrix antifouling
The coat’s high levels of insoluble resin make it hard and stop erosion. The resin is packed with active ingredients, and the particles are so close that as one dissolves the next is exposed. Hardness and durability makes these antifoulings ideal for fast power boats, mud-berthed vessels and racing yachts (burnishing the antifouling with wet abrasive paper before launch gives a smooth finish).

NB : There are additional types of antifouling for specific use : Aluminium (with or without copper), propeller, inflatables & RIBs,…

Preparation of antifouling application
Preparation of the hull : It’s important to organise your boat maintenance in accordance with the product application time needed and further delay is recommended before returning the boat to the water.

  • On previously antifouled surface : Clean the entire hull with controlled high pressure washing or brush, and remove old layers of antifouling.
  • On new hull : The surface should be degreased with Nautix SD, rinse with fresh water, let dry, wet-sanding , and apply adapted adhesion primer. 

Before painting; cover the waterline with masking tape and protect all parts that must not be painted (sensors, anodes…).
Paint application; antifouling is usually applied with a roller or a brush but one can also use a spray gun to achieve a smoother surface (for racing hulls.)
Apply minimum 2 coats, not too thickly. Antifouling efficiency depends directly on applied film thickness. 

Advantages & Inconvenient of different types of antifouling
Hard matrix antifouling :
+ Very good resistance to abrasion, sand, beaching, or transport over trailer.

+ Recommended for areas with tide or for long-crossing boats.
+ Solid & durable through whole season
+ Very resistant to polishing and scratching
- Needs to be abraded after the season(maintenance).
Self-polishing antifouling :
+ Controlled release of active substances throughout the season.

+ Works gradually throughout the season.
+ Easy maintenance with minimum preparation time.
+ Polished itself with boat speed (friction with water).
+ Gives constant performance (smooth, clean,…) throughout the season.
- Not suitable for long-crossing boats or boats with long non-sailing period.

Some important rules to respect for antifouling maintenance :

  • Before any new application, the surface must be in good condition, dried, degreased and free from contaminates.
  • If you are using hard-matrix antifoulings, it’s possible to see an exhausted layer of resin at the end of the season. It’s recommended wet-sanding surface before application of new antifouling.
  • Self-polishing antifoulings can be applied directly over old substrate. First the surface should be degreased with Nautix SD and free of all contaminants (oil, grease, salt etc). It’s necessary to remove all loosely adhering and flaking paint. Then rinse with fresh water and let dry. Once dried, new antifouling can be applied.
  • A traditional/soft antifouling should be sealed with Nautix P1 Primer before applying an erodible or hard antifouling on top of it.
  • If you don’t know technical features of old antifouling, it must be overcoated with Nautix barrier coat P1 to avoid any problem of compatibility. If you are facing loosely adhering and flaking paint, it’s strictly recommended to remove old layers (by sanding until layer of primer) before application of new antifouling.
  • Do not apply when there is a chance of condensation forming on the substrate : substrate, ambient air and product temperatures must be close.
  • It’s important always to give antifoulings a good stir with a bladed instrument before applying, as they contain heavy pigments which can settle.
  • Antifouling efficiency depends directly on applied film thickness. Apply the whole recommended quantity (excl. thinner) : 2 thick layers and 3rd layer on leading and trailing edges (waterline, keel, rudder,…), where water flows strongest.
  • Be careful when adding solvents to antifouling as this will reduce the thickness applied.
  • Never dry sand old antifouling, as the dust is toxic.