En­vi­ron­men­tally Friendly Below the Wa­ter­line

Passage Maker - - Troubleshooter - BY STEVE ZIMMERMAN

Over the past five years, bot­tom­paint man­u­fac­tur­ers have made great strides in cre­at­ing ef­fec­tive an­tifoulants that greatly re­duce im­pact on the en­vi­ron­ment. Se­lect­ing a “green” bot­tom paint no longer means choos­ing a less ef­fec­tive one. Be­fore we look at the op­tions, let’s take a brief tour of the his­tory of bot­tom paints on boats.

A papyrus doc­u­ment from the 4th cen­tury B.C. ref­er­ences the use of ar­senic mixed with sul­phur and oil to pre­vent foul­ing. In the 14th cen­tury, Chi­nese ad­mi­ral Cheng Ho or­dered the hulls of his junks coated with lime juice mixed with poi­sonous oil. In 1625, a Bri­tish in­ven­tor patented a paint mix­ture that in­cluded cop­per and iron pow­der. Both in­hib­ited marine growth. Since that pa­tent, ver­sions of cop­per-based paints have dom­i­nated the mar­ket. Tributyltin, or TBT, en­tered the scene in the 1950s.

By the 1980s and ’90s, TBT ran into reg­u­la­tory ban­ish­ment, be­cause the ef­fects of TBT paint go be­yond the or­gan­isms that it is in­tended to kill. By poi­son­ing bar­na­cles, al­gae, and other or­gan­isms at the bot­tom of the food cy­cle, TBT works its way up the en­tire marine food chain. It has been shown to harm­fully af­fect many lay­ers of the ecosys­tem, in­clud­ing in­ver­te­brates and ver­te­brates—even hu­mans.


Bot­tom paints af­fect the en­vi­ron­ment in two ways: or­ganic com­pounds evap­o­rat­ing into the air and chem­i­cals (mostly cop­per) leach­ing into the sea.

If you have been around a freshly painted bot­tom, you know about the strong odor. The smell is caused by sol­vent evap­o­rat­ing from the wet paint, al­low­ing it to dry.

Th­ese sol­vents con­sist of volatile or­ganic com­pounds, or VOCs, which can be harm­ful to hu­man be­ings and to the en­vi­ron­ment as a whole.

By chang­ing to wa­ter-based for­mu­las, chemists and paint man­u­fac­tur­ers have

re­duced VOCs in an­tifoul­ing paints by roughly 75 per­cent. In ad­di­tion to greatly re­duc­ing VOCs, th­ese prod­ucts can be cleaned up with soap and wa­ter with out con­tam­i­nat­ing wa­ter around the boat­yard.

Re­mov­ing cop­per presents an­other chal­lenge. For many years, boat own­ers se­lected the heav­i­est gal­lon of bot­tom paint, rea­son­ing cor­rectly that heav­ier paint meant more cop­per, some­times more than 70 per­cent by vol­ume. While the harm­ful ef­fects of cop­per are far less cer­tain than that of TBT, high con­cen­tra­tions found in har­bors caused con­cern.

In 2011, Wash­ing­ton State passed leg­is­la­tion that will grad­u­ally elim­i­nate bot­tom paints con­tain­ing more than 0.5 per­cent cop­per. In the past few years chemists found a way to re­move the cop­per, re­plac­ing it with Econea, a met­al­free phar­ma­ceu­ti­cal for­mu­la­tion. Econea is biodegrad­able, non-cor­ro­sive to dis­sim­i­lar me­tals, and has even been FDA-ap­proved for dan­druff sham­poos. In­stead of uti­liz­ing a makeup of 50 per­cent cuprous ox­ide, a so­lu­tion with only 6 per­cent Econea af­fords equiv­a­lent level of pro­tec­tion.

Both cop­per and its equiv­a­lent, Econea, max­i­mize their ef­fec­tive­ness on hard growth, such as bar­na­cles. The area along the wa­ter­line tends to ac­cu­mu­late slime, or soft growth. Many cop­per­based bot­tom paints in­cluded a chem­i­cal known as Ir­garol to deal with slime. In 2015, BASF, the com­pany that pro­duces Ir­garol, sur­prised the marine in­dus­try by an­nounc­ing that this al­gae­cide would not be avail­able. No date has been set for its rein­tro­duc­tion, as a com­bi­na­tion of en­vi­ron­men­tal com­pli­ance is­sues and pro­duc­tion de­ci­sions have stopped the process. Zinc-based ad­di­tives have stepped in to pro­vide a sim­i­lar re­sult.

When it comes to en­vi­ron­men­tally safe bot­tom paints, boat own­ers have three op­tions: low VOCs and no cop­per (small­est en­vi­ron­men­tal foot­print), low VOCs with cop­per, or higher VOCs (though still EPA com­pli­ant), with cop­per (largest foot­print). Prices dif­fer, and some prod­ucts have ad­van­tages over oth­ers, de­pend­ing on use and re­gion. None­the­less, it is now pos­si­ble to have a highly ef­fec­tive bot­tom paint with min­i­mal, neg­a­tive en­vi­ron­men­tal im­pact. When ap­ply­ing a wa­ter-based paint for the first time, pay close at­ten­tion to the in­struc­tions on the can. Check com­pat­i­bil­ity with the ex­ist­ing coat­ing on

your boat, and pay at­ten­tion to the type of roller, thick­ness of coats, and dry­ing times. A more con­ven­tional paint might call for a 3/ 8- inch nap roller, while the wa­ter-based might spec­ify 3/ 16.

When choos­ing bot­tom paints, chem­i­cal com­po­si­tion mat­ters: More Econea and more zinc trans­lates into bet­ter an­tifoul­ing prop­er­ties. No dis­cus­sion of bot­tom paints would be com­plete with­out ex­plor­ing one more area of emerg­ing tech­nol­ogy. A num­ber of com­pa­nies now of­fer an­tifoul­ing sys­tems based on ul­tra­sound. Trans­duc­ers at­tached to the in­side of the hull emit low-wattage ul­tra­sonic pulses that res­onate through the lam­i­nate to the outer sur­face, pro­duc­ing mi­cro-cav­i­ta­tion bub­bles. Th­ese bub­bles dis­rupt the cel­lu­lar struc­ture of marine mi­cro-foul­ing. Th­ese sys­tems do not claim to re­place bot­tom paint; they ex­tend the paint’s life and ef­fec­tive­ness.

A source of power must be avail­able, whether from shore­power or so­lar pan­els. Hulls cored below the wa­ter­line re­quire spe­cial care: The core must be re­moved for each trans­ducer and the area lam­i­nated so that the trans­ducer di­rectly con­tacts the in­ner sur­face of the outer skin. Most cruis­ing power­boats end the core at the wa­ter­line, and in those cases, no ad­di­tional work is needed. The num­ber of trans­duc­ers needed de­pends on ves­sel size and con­fig­u­ra­tion. A 40-foot trawler would need four to six trans­duc­ers, de­pend­ing on the prod­uct cho­sen and hull shape. Run­ning gear pro­tec­tion re­quires ad­di­tional trans­duc­ers.

En­vi­ron­men­tal pro­tec­tion can be a thorny topic, with un­clear an­swers and com­plex choices. You will pay more for a gal­lon of low-VOC, cop­per-free paint, but you won’t sac­ri­fice ef­fec­tive­ness and you will be keep­ing the air and wa­ter cleaner.

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