Zinc stink

There are friend­lier al­ter­na­tives to zinc an­odes.

Boating NZ - - Contents - BY CRAIG RITCHIE

Elec­tron­ics are al­ways ex­cit­ing, en­gines can E be a thrill, even moor­ing lines and an­chors catch pass­ing glances in the chan­dlery. But let’s be hon­est, most boat­ies don’t give a sec­ond thought to their sac­ri­fi­cial an­odes – those cu­ri­ous knobs of raw metal found on out­drives, shafts, rud­ders and other metal com­po­nents that dan­gle un­der a boat.

We know that the an­odes pro­tect those im­por­tant metal bits from cor­ro­sion, and we know that over time they will wear away and need to be re­placed. But be­yond that, no one ever gives them a sec­ond thought.

That’s too bad, because an­odes are ac­tu­ally pretty amaz­ing things. Metal parts that re­main sub­merged un­der the wa­ter tend to cor­rode quickly as a re­sult of nat­u­rally-oc­cur­ring elec­tro­chem­i­cal re­ac­tions. An­odes are made from spe­cial metal al­loys that have a par­tic­u­larly at­trac­tive elec­tro-chem­i­cal volt­age range, caus­ing these cor­ro­sive re­ac­tions to fo­cus on the an­ode in­stead of the ad­ja­cent metal com­po­nents.

The prin­ci­ple is a bit like cater­ing for a kid’s birthday party by serv­ing cake and broc­coli at the same time – the cake gets de­voured while the broc­coli es­capes un­touched. It’s a sim­ple ap­proach that works equally well on small boats, large yachts,

We have to let peo­ple know there are al­ter­na­tives to zinc that are safer to use...

com­mer­cial ships and even shore­line in­stal­la­tions like sea walls and lock gates.

An­odes have his­tor­i­cally been made from zinc-based al­loys – to the point where they’re more com­monly known as ‘zincs’ than by their proper name. While zinc is an ef­fec­tive an­ode ma­te­rial, in re­cent years its use has come un­der the microscope in light of mount­ing ev­i­dence that the stuff causes real prob­lems when found in high con­cen­tra­tions, such as in the wa­ter around mari­nas.

In the US, wa­ter test­ing in the vicin­ity of large ma­rina fa­cil­i­ties in Cal­i­for­nia, Wash­ing­ton and Delaware has con­sis­tently yielded sam­ples show­ing sig­nif­i­cant lev­els of zinc. What’s con­cern­ing is that while small amounts of zinc are con­sid­ered essen­tial for hu­man health, new re­search sug­gests that ex­po­sure to high con­cen­tra­tions of it could be linked to a va­ri­ety of se­ri­ous health con­cerns. That con­tention is sup­ported by a grow­ing body of ev­i­dence in­di­cat­ing that pro­longed ex­po­sure to high lev­els of zinc is toxic to a wide range of aquatic plants, in­ver­te­brates and fish.

What’s worse, zinc an­odes fre­quently con­tain ad­di­tives like cad­mium, an el­e­ment that has been con­clu­sively as­so­ci­ated with se­ri­ous ill­nesses in­clud­ing kid­ney dis­ease, ath­er­o­scle­ro­sis, hy­per­ten­sion and car­dio­vas­cu­lar dis­eases. Cad­mium has also

LEFT Zinc an­odes can cause en­vi­ron­men­tal dam­age when pre­sent in large num­bers, such as in mari­nas. Alu­minium or mag­ne­sium an­odes are kin­der to marine life.

BE­LOW & BOT­TOM LEFT They do their job well, sac­ri­fic­ing them­selves for the good of your boat. But there are al­ter­na­tives to zinc an­odes.

Newspapers in English

Newspapers from New Zealand

© PressReader. All rights reserved.