How to Remove Mildew from Inflatable Boat Cover

Skipper July 6, 2009 Ask The Skipper

Lou Dietrich asked:

I’ve been referred to your company by allinflatibles.com

About 2 years ago, I purchased a cover for my Zodiac from you (allInflatables.com) and it has held up very well; however it is now mildewed over most of the cover, inside and out

Is there a product I can use to remove the mildew? Can it be ‘machine’ washed with any product? I am looking for a product to clean and resist mildew from my Zodiac boat cover.

Answer:

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IN QUICK SUMMARY:

To Clean and Remove Mildew from Inflatable Boat Covers,

Stretch out the boat cover
Wet it with garden hose
Spray Boat Clean Plus over the surface
Work it in with a medium to light scrub brush
Let it stand for 15 to 20 minutes
Rinse Clean
Repeat on the other side

IN MORE DETAIL:

I assume that your cover is made of polyester canvas.

A good product to clean and remove the mildew is Aurora Boat Clean Plus. It’s a heavy duty, water activated cleaner, which is safe for all surfaces, including soft surfaces like canvas. It’s free rinsing so it will not leave any residue behind, like soap or detergent scum which is food for mildew. A good way to clean the cover is to stretch it out, over the boat, or on the dock, wet it with a garden hose, spray Boat Clean Plus over the surface and then work it in with a medium to light scrub brush. Be sure to pay particular attention to seams and areas where straps or attachments may be sewn on.

Let it stand for 15 to 20 minutes and rinse it clean. Flip the cover over and repeat on the other side. If the mildew growth was heavy; i.e. all over the cover, repeat the process, first on the top and then the inside. Allow the cover to dry thoroughly, preferably in the sun.

NOTE: If mildew stains remain, stretch the cover out in the sun for several days or even weeks to allow the sun to bleach out the stains. Cleaners and chemicals strong enough to remove the stains can also damage the canvas and stitching and will shorten the life of the fabric and should not be used, except as a last resort. If the above procedure does not remove the stains, try a mild solution of Hydrogen Peroxide and water or Oxygen Bleach, but keep in mind that you may remove color and damage the fabric. Afterwards re-wash the cover with Boat Clean Plus to remove any residue.

Machine washing is not necessary, but if you do use a washing machine, be sure to use cold water and a gentle cycle and re-wash 2 or 3 times. Be aware that machine washing can damage elastic and straps or fittings that may be sewn onto the cover.

There are over 100,000 strains of Mold Fungi, commonly known as Mildew. They are present in the air from count concentrations of 100 to 1,000 per M³. They need oxygen, water, a food source, stagnant air and a narrow temperature range to grow. Ideal temperature is 70ºF to 90ºF but they grow at other temperatures. Freezing causes them to become dormant, but will not kill them. Food can be starches, proteins, oils, pollens and bacterial and sufficient quantities can be found in surface dirt, soap scum, body or suntan oils transferred to the cover etc.

The best way to prevent future return of mildew is to remove as many life sources as possible. Keep the cover clean. Wash it with a free rinsing cleaner like Boat Clean Plus that will not leave soap scum behind, at least once a year. When covering the boat, use a pole to keep the cover up and allow water to drain off. Make sure that there is ventilation under the cover. If the cover does not have ventilators sewn in, use something like foam blocks or strips on either side of the boat or stern and bow, between the cover and the boat. This allows the air to circulate and remove dampness. If the boat is in storage, store it in a dry area where there is some air circulation. Oftentimes boat owners will keep a 100 watt light bulb burning in the cabin to remove dampness during storage or put a small low wattage fan in the boat to keep the air circulating.

Your other concern should be the Zodiac. If you have mildew on the cover then the boat is very susceptible to transfer and contamination of the mildew. I recommend that you clean your inflatable with Speed Clean and protect it with Poly Guard. If you do get mildew growing on the tube, you will be able to remove it before it attacks and stains the fabric. Depending on the type of boat you have and how you use it, you may also want to apply Repelin and Sure Step to your boat. These products are recommended by Zodiac.

Thanks for your question,
Captain Aurora