SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

How to treat bilge mold/mildew before painting

3K views 10 replies 10 participants last post by  FreeAgent 
#1 ·
Hello All,

I've scraped the old paint off the interior of my hull of my 1968 Tempest, underneath the cockpit and under the floor boards. Underneath the floorboards up front there is what I think is some mold and mildew. There was a leak from the pulpit stantions (repaired now I believe). The pictures give some detail.

I plan to paint the whole area with Jamestown Distributors Total Boat Bilge Paint but thought I should try to treat some of the mildew before applying the paint.

I'd appreciate any suggestions on the best treatment? Any special spray to use on this fiberglass? should I try to air it out and get some sunlight in for a few weeks? Is it dangerous to put paint over this area as it would trap in the mildew?

Thanks as always,
Alan
 

Attachments

See less See more
4
#2 · (Edited)
Suggest you use TriSodiumPhosphate-TSP a caustic used to clean wood in preparation of painting; any sodium silicate based detergent which also a caustic, etc. etc.
Caustics will dissolve the fungal cells and their spores. Soak time is important; the longer the better, then 'scrub'. Make up a strong 'saturated' solution and apply, or 'spritz' and let soak, scrub and then thoroughly rinse. Consider to use a power washer to remove the rest of the adhering gunk before painting. These caustics will also 'lift' most paints ... so use a wet/dry shop-vac to suck up the remnants of the lifted paint from the bilge. To prevent or retard re-infection, clean the underside of any floor pans, floor boards, or other hidden spaces, etc. if possible.

TSP is cheap and relatively inexpensive, available in powder form from paint and hardware stores; you mix it into water until no more 'crystals' will dissolve.
Sodium silicate based caustic detergents are available from boat chandleries: eg. "Roll-Off™", etc. - relatively expensive. Caustic spray-on 'oven-cleaners' can also be used for difficult to clean places.
Be sure to use protection when using these caustics as they can also dissolve skin, and eyeballs, etc.
IMPORTANT - Always use a full respirator when cleaning any 'dark' or black-ish fungal - some of these are very dangerous to your respiratory system - stochybotris atra is VERY bad and is often confused with 'mildew', it commonly thrives in wet places. Only 'clean'/scrub fungals that are WETTED; 'Dry' cleaning will release and spread the spores.

Once your new paint is well cured and thoroughly dried, consider to regularly apply 3M Mildew-Block™ to keep the fungal population under control ... it will kill airborne fungal spores that happen to land/settle on it.

Edit/Add - All the above is predicated upon that you need to REMOVE the mold/mildew and not simply kill it. Killing it will not remove it, and the 'remnants' will only ultimately become the nutrient source of other fungals.

;-)
 
#9 · (Edited)
Another big fan of tea tree. Have some in both heads and in all unvented lockers. Buy the big bag (~$72) Ends up being cheaper. Can use any plastic jar with a few holes drilled in the top and upper sides as dispensers. Find it's worth the extra money to get the brand name Kanaberra gel. But you first need to clean. Depending on what you have for tanks and other things in you bilge you may not want to use strong acids ( roll on-off) or caustics and leave them in. TSP is usually safe however.
Have turned off the bilge pumps mixed up vinegar (weak acid), then dawn ( will foam so not too much).Then flood bilge with fresh water and more dawn with some Calgon. Leave in for a few days while going sailing. Then a deck brush to agitate and clean all surfaces you can reach. Flush repetitively using fresh and bilge pumps until no foaming. Tough spots of dug in mold come up with rubbing alcohol which won't etch metals.
Before painting turn on AC with bilge boards up to make things really dry or wait for several hot low humidity days. Add anti fungal to paint ( sold in any paint store).

Current boat has built in glass tanks so muriatic acid ( wood bleach), a bit of dawn and a good sail to windward works just fine.

Sucky job as to do really right you need to get in all the nooks a crannies. We did this to a T37. Needed to nearly empty everything out of the boat and do some deconstruction to get at all the spots both for cleaning and then painting. But got rid of all the smell.
 
#10 · (Edited)
I used diluted 12% Clorox and wiped after a few minutes. The bilge paint was excellent at covering and adhering. By the way I used white bilge paint to brighten the areas being painted instead of gray from the factory, easily cleaned. Added a couple of LED lights to the lazarettes and everything looks great and very bright. I painted under settees also. Easy job and well worth the effort.
 
#11 ·
Two issues here it seems.
- removal of mold to prepare surface for painting
- kill and prevent future mold

Regardless of mold, bilge surfaces need to be cleaned and prepared before painting. On inside of glass hull, a thorough cleaning should get rid of it (mold doesn't usually form much on fibreglass anyway)

Haven't had mold on our boat, but at house used this spray type product. Mold Control Spray - Concrobium

For initial degreasing of hull surfaces, used Simple Green Surface Prep. It is biodegradable so should be no problem if it gets into water. https://www.sherwin-williams.com/homeowners/products/simple-green-surface-prep-cleaner.

Then sanded lightly with 80-100 grit to give the surface some edge. Then painted with Interlux Bilgekoat. Bilgekote Topside Paint | Interlux Usually one coat did it!

In some areas under engine it was hard to clean well, but the Bilgekote seemed quite tolerant of my not so perfect cleaning. It is a great paint to use. Covers well, dries quickly and looks good once done. I use the grey because it doesn't look as bad as white when dirty!
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top