Aluminium Powder Coatings and Epoxy Primer Finishes

Saildrives are especially critical underwater surfaces when it comes to maximizing fuel efficiency and avoiding top speed degradation. Here we discuss how to keep your saildrive barnacle-free and in excellent condition year after year.

Marlin Yacht Paints Velox Plus has been found to achieve excellent results in keeping Aluminium surfaces free from fouling. The system, when done right, results in a tough (including running over the odd line or other water debris) and durable solution you can easily service yourself 

• in-between haul-outs with a quick dive and a rag in hand (if needed) and  
• at haul-out without needing to grind or heavily sand.

Noting that a 'quick dive with rag-in-hand' can be problematic and is worth taking a moment to talk about;

• when cleaning an ablative surface; a plume of black water smoke quickly appears and the value of the 'quick dive' is even more quickly questioned,
• when cleaning a silicon-based foul release specialist equipment is required, the delicate silicon membrane needs to be managed by a trained expert,
• however Velox Plus is a hard and durable surface that is neither of the above.

Before getting started, as always, no two boats situations are the same, and there are so many factors - water temperature, flow, salinity, renewable energy & shore-based electrical discharge from both the vessel and others around, to name but a few - but typically if you do the preparation then the data points suggest you will be successful. Of course the best way to mitigate these environmental effects is regular boat use &/or regular cleaning via a dive.

To begin ... let's first check with the manufacturer, at their site Marlin Yacht Paints

PARTS COATED WITH FACTORY PAINTS: The stern-drives and other aluminium parts are normally treated with factory paints. These should not be removed. Degrease, sand lightly with fine paper or abrasive felt, then prime with METAL PRIMER.

So what does this mean in practice? This advice applies to both factory powder coated and epoxy primer coated surfaces. As much as this applies to saildrives it also to other areas having same surface finish, for example gantry engine mountings or the leading edge of outboard engine where the front tip is prone to dipping into the water from time to time.

What to use? For factory powder-coated surfaces, Scotch Brite pads as shown or 180-220 grit sandpaper. For epoxy primer coated surfaces, 180-220 grit sandpaper.

Any exceptions? Yes. If you are applying an epoxy primer as part of the application read their TDS but typically you have an over-coating window (e.g. 3-7 hours at 25 degrees). Aim to apply Marlin Yacht Paint's Metal Primer within this window. If you miss it, prepare the surface with 180-220 grit sandpaper.  

What next? Once the surface is prepared the next steps are; 

• Apply Marlin Yacht Paints Metal Primer, one coat
• Apply Marlin Yacht Paints Velox Plus, three coats
• Noting
• • At 20 degrees wait 3 hours between coats and 12 hours prior to launch (at 30 degrees this becomes: 2 hours/8 hours)
  • Time permitting, ideally aim for a coat a day
  • Both paints can be brushed, rolled or sprayed
  • Find more great advice at the manufacturers application page, here

Where does it go wrong? Here we see a year 2+ reapplication, with plenty to learn.

• The factory coating has been attacked by a grinder with a flapper disc needlessly. Likewise the prop, stripped and brightened ... but that's a discussion for another post. 
• Leading to exposed aluminium in parts

Lack of protection exposes the underlying aluminium to the corrosive elements in marine environments. Saltwater, moisture, and oxygen can cause aluminium to corrode, leading to pitting, weakening, and eventual failure of the saildrive. Not to mention voiding the warranty.

From here what do you do? The Gold Standard is to get the surface re-coated. Alternatively strip back to metal and apply an epoxy primer, typically three coats at a minimium. Bear in mind that aluminium will start to oxidise within a few hours of exposure, so you need to have that first coat on in time.  The aluminium leg must be abraded with 60/80 grit prior to epoxy priming.

What if I have previously used a silicon-based foul release like PropSpeed? Remove the foul release, then; 

• Wash thoroughly with a strong solvent and or wax and grease remover to remove any contaminants, and 
• Sand with 80 grit sandpaper, followed by 
• Application of Boating Products Etch Primer, one thin coat, before
• Then applying Marlin's Metal Primer & Velox Plus, as noted above  

What happens in Years 2+? Again, let's consult the manufacturer's site in regard to preparation;

SURFACES ALREADY TREATED WITH VELOX PLUS IN GOOD CONDITION: Pressure wash with fresh water and/or sand very lightly with fine paper or abrasive felt. Leave to dry well.

At this point we are back into the cycle;

• Touch up as needed with Marlin Yacht Paints Metal Primer, one coat
• Apply Marlin Yacht Paints Velox Plus, three coats
• Noting
• • Every 3-6 years aim to completely remove the Metal Primer & Velox Plus and reset. Typically, if the majority of paint is still in place then this is not needed.

If you have any specific questions about product or application, please reach out to us at info@boatingproducts.com.au. 

In Australia you can purchase Velox Plus by visiting one of our Stockists, click here https://www.boatingproducts.com.au/stockists or online at our shop here.

Happy Boating!