Summary for biocides in marine coatings Discussion
biocides in marine coatings are discussed here as a difficult tradeoff between performance and environmental impact. Karthik Suryanarayanan asks what typical biocides are used in marine coatings and steel pipes, noting that silver is too toxic and that copper in some marine coatings may be phased out because of harm to marine life. The reply says copper-based bottom paint is still widely used and not really being phased out, citing Boat U.S. listings as evidence. The answerer argues that asking for an “environmentally friendly” paint that kills marine organisms is inherently contradictory, though organic biocides that lose toxicity over time would be preferable to metals like copper, which may remain toxic long after they wear off. The response also warns that organotin paints, especially tributyltin, were an environmental disaster. The practical advice is that any biocide should ideally become non-toxic after a limited period.
Q. Hello,
I am a graduate research assistant at the University of Cincinnati, I develop novel organic coating systems using silanes. I am studying paint systems that have biocides or microbicides such as silver incorporated in them to address the issue of microbial corrosion. I read in an article that Cu used in some marine coatings is being phased out as it is detrimental to marine life. I want to know what is a typical biocide used in marine coatings and also in steel pipes, silver is out of the question as it is toxic. Are there any environmentally-friendly organic mild biocides being used by the coatings industry?
Thanks,
Karthik Suryanarayanan
organic coatings – Cincinnati, Ohio
2004
A. Hi, Karthik. It is possible that copper-based “bottom paint” may be outlawed, I guess, but it isn’t exactly being ‘phased out’. As far as I can see, every single brand and style of bottom paint listed in the Boat U.S. catalog is copper-based and depends upon copper.
It is more than a conundrum to look for an ‘environmentally friendly’ paint that will kill every form of marine life from algae to zebra mussels–it’s an oxymoron. But it sounds like organic biocides, which might stop their killing after a few years, would be better than basic metals like copper which can presumably remain toxic to marine life even decades after they’ve sloughed off the bottom of the boat and onto the bay floor. On the other hand, though, organotin paints (tributyltin) have been an environmental disaster. Whatever you put in the paint as a biocide should, I would think, completely lose its toxicity after some period, perhaps depending upon the proximity of two different molecules that can be depended upon to break or not remain in proximity after the paint wears off.
You have certainly picked an interesting and important field to do your development work in. Good luck!
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
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2004