How to prepare and apply Antifoul to your vessel

This guide is here to help you prepare and apply antifouling to your vessel. The guide is based around our Altex range of products. If you buy one of our other range of Antifouling products please follow the directions on the can that it comes in. For more details or advice please feel free to contact us.

How to Antifoul your boat

STAGE  1
Surface Preparation

Thorough surface preparation is the secret to the success of the antifouling job you are about to undertake. Well applied coatings will protect your boat from marine growth, and protect your hull from the harsh salt water environment. Poor preparation & workmanship result in poor performance, coating failures and expensive repairs.

WATERBLAST
The surfaces to be painted to remove salts, slime, marine growth & failed coatings. The higher the water pressure you can use, the better, as this will reduce your overall workload. Ideally pressure should be 3,500 – 4,000 psi.

SANDING
After Water cleaning, all antifouled surfaces should be thoroughly wet sanded with 80 grit wet & dry paper using a pole sander to remove any remaining, hydrolysed (spent) antifouling and residual slime. Rinse thoroughly to remove all sanding residues. The sanded surface, once dry, should be free of any antifouling dust, free of residual slime, and a clearly discernible surface profile should be evident in the aged coatings. (For conversion from other antifouling brands to Vivid, ensure the wet sanding operation is even more thorough to enhance adhesion.) Use a disc grinder, soft pad, orbital sander, or similar, with an 80 grit (non-metallic) pad to remove:
• any broken or sharp edges, so that all coatings have bevelled edges.
• any blisters and sand back pitted areas
• all poorly adhering coatings
• any crazy cracking
AND ENSURE:
• all exposed old primers/undercoats are abraded
• all exposed substrate is well abraded to achieve a clearly discernible surface profile. Both steel and aluminium must exhibit clean, bright metal, again with a well defined surface profile. Avoid polishing the surface. Pay particular attention to the waterline area, where the wet/dry cycle, and the exposure to the sun causes the antifouling to crazy crack. Sand these areas thoroughly.

DEDUST
With either clean compressed air, vacuum or use a clean soft brush. Do not use rags to dedust as any lint that “hooks” onto the surface may create a wick that can interfere with coating performance.


STAGE 2 
Antifouling of Fibreglass, Gelcoat, GRP, Mild Steel &Timber

PRIMING
Apply 2 to 3 spot coats of the selected primer to all bare substrate and to any aged, abraded primers – more if the old coatings are deemed to be very thin.
Epoxy Barrier Undercoat is ideal for direct application to Fibreglass, Gelcoat/GRP. To achieve adequate barrier protection, Epoxy Barrier Undercoat may also be applied over surfaces primed with Epoxy Primer. For wooden surfaces that have not been pre-sealed, we recommend the first coat of primer be thinned 30% to aid penetration into the wooden surface. Some woods are more porous than others and will require an additional thinned coat.

PAINTING
Once the primers / barrier coats have been applied, the first coat of No.5 Antifouling can be applied. We recommend repainting the “spot repaired” areas first to seal them within the recommended timeframes.
IMPORTANT: Timing of the application of the antifouling onto the last coat of Epoxy Primer or Barrier Undercoat is critical. Solvent entrapment from coating too soon, or poor adhesion from coating too late are very real possibilities.
Below are the recommended times for the Altex range of primers to apply solvent borne antifoulings:

PrimaShield Antifouling Sealer  Minimum 6 hours  Extended maximum to 30 days
MultiPurpose Primer Minimum 24 hours Extended maximum to 30 days
Epoxy Primer Minimum 2 hours See note 1. below
Altex Epoxy Barrier Undercoat * Minimum 2 hours  See note 1. below

Note 1:  Epoxy Primer or Epoxy Barrier Undercoat* should still be slightly soft prior to overcoating with antifoul i.e tack free but still soft to the touch/finger printable.
Now the hull is fully coated in either new or aged antifouling, the subsequent coats may be applied any time in the next few days.
All aluminium propulsion systems will need to be coated in Vivid Antifouling. It is recommended that Vivid Antifouling be applied in a radius beyond the alloy fittings to ensure no traditional cuprous oxide antifouling comes into close contact with any alloy surfaces. See below.

Antifouling of Aluminium
Vivid Application

PRIMING
Apply Epoxy Primer to the exposed alloy surfaces within 2 hours of preparation. Apply 2 to 3 spot coats of Epoxy Barrier Undercoat or Epoxy Primer to all newly primed areas and to any aged & abraded old primers, more if the old coatings are deemed to be very thin.

PAINTING
Once the primer / barrier coats have been applied, the first coat of Vivid antifouling can be applied – we recommend repainting the “spot repaired” areas first to seal them. Please follow these guidelines when painting aluminium stern drives or other alloy surfaces below the waterline. 
 
Vivid® antifouling may be applied to any of the below waterline primers listed in this brochure, and may be applied to any hull type, made from any of the typical construction materials. IMPORTANT:  Timing of the application of the antifouling onto the last coat of primer is critical. Solvent entrapment from coating too soon, or poor adhesion from coating too late are very real possibilities
Below are the recommended minimum & maximum times for the antifouling to be applied to the selected primer:

Epoxy Primer Minimum 2 hours See note 1. below
PrimaShield Antifouling Sealer Minimum 6 hours Extended maximum to 30 days
Epoxy Barrier Undercoat* Minimum 2 hours See note 1. below

Note 1:  Epoxy Primer or Epoxy Barrier Undercoat* should still be slightly soft prior to overcoating with antifoul i.e tack free but still soft to the touch/finger printable. (*or other Altex Two Pack Epoxy Coatings)
Some grades of aluminium are reactive with virtually all cuprous oxide free antifoulings, such as Pettit Vivid®
To avoid any reaction at the masking line between bare alloy surfaces and the Vivid waterline, it is recommended that an insulation zone be installed. Once two coats of Epoxy Primer have been applied and cured at the waterline, lower the masking tape approx. 25mm before applying the final coat of primer and the Vivid antifouling.


DISCLAIMER The recommendation’s provided on this website have been suggested in good faith based on common and assumed information that would be typical of the given situation. Altex Coatings Ltd has taken all reasonable steps to ensure the recommendations meet the needs of the typical client/situation but reserves the right to amend or withdraw any recommendations due to a change in conditions. If the steps outlined are not followed correctly or should the starting surface not be of a repairable state then Altex Coatings and Mister Antifoul does not take any responsibility for failure of the product to perform as pictured.