Marine Galvanic Corrosion Made Easy. - Batemans Bay

Marine Galvanic CorrosionMade Easy.Brought to you by Marine Protection Systems Pty Ltd

IntroductionMade possible by the generous invitation and support ofSandringham Yacht ClubPresented and Supported byMarine Protection Systems – Jeff BullockLogix Group – Brian Gatt

Seminar ObjectivesUnderstand and identify:Common issues including electrolytic corrosion (electrolysis), galvaniccorrosion, growth, paint blasting and timber rot.How a bonding system works, learn how to repair andmaintain an efficient bonding network.Appropriate anode selection.Strategies to prevent corrosion, marine growth and reduce on-goingrepair and maintenance expenses.Understand international standards and industry best practice.

Types of CorrosionTwo basic types of corrosion for primary concern:1.Electrolytic Corrosion; is stray current induced and often referred to asElectrolysis.2.Galvanic Corrosion; relies on two dissimilar metals connected and in thesame electrolyte (sea water).

Other Common IssuesSecondary effects of poor corrosion protectionThese other common issues are all related to cathodic protection and are alsopreventable:Paint blastZinc passivationWood rotExcessive growthDezincificationGalvanic coupleRefer Corrosion ID poster for picture and explanation

Electrolytic CorrosionWhere did my prop go?

Electrolytic CorrosionWhat isCaused by stray currents from apower source:Faulty or damaged wiringleaking current.Faulty on board device leakingcurrent.Shore power connection / nogalvanic isolation.

Electrolytic Corrosion

Electrolytic CorrosionShore PowerPlugging in to marina shorepower connects your vesselssubmerged metal to others inthe marina via the commonearth conductor.Unless isolated, your vessel canreceive damaging current thatwill prematurely destroy anodesand then put your expensivemetals at risk.Isolate your vessel with anElectrolysis Blocker installed bya marine electrician.

Electrolytic CorrosionOn boardA damaged appliance orwiring that is leakingcurrent to ground via thehull (metallic hulls) or viacommon earth tosubmerged metal is causingElectrolytic Corrosion (EC).EC can also rot bearings,washers, oil and watercoolers and cause majorengine damage quickly.

Electrolytic CorrosionPreventionYou can very easily make quickobservations to see if your vessel isor could be suffering fromElectrolytic Corrosion. Look for signsof obvious action or leakage like thewiring pictured here.A qualified marine electrician canperform an earth leakage test fromthe marina or on board electricaldevices.For real piece of mind and cheapinsurance schedule an annual ortwice annual earth leakage test.

Galvanic CorrosionCaused by dissimilarmetals in contact andin the same electrolytewith out anodeprotection.Stainless screws usedon aluminium keelslipperPREVENTABLE

Galvanic Corrosiondezincification or pinkingCaused by dissimilar metals incontact and in the same electrolytewith out anode protection.Here the manganese bronze rudderhas started wasting to protect themore noble metals it is connected tolike stainless steel.Many people would paint over this,however critical structural damagehas been done. This rudder will notperform as intended and could evenbreak.PREVENTABLE

Galvanic CouplingVery common sight internallyaround skin fittings. Seen here ona toilet intake that has stainlessthrough hull, bronze gate valveand custom stainless top fitting.No bonding connection exists toan anode so a local galvaniccoupling as been established.PREVENTABLE

Secondary IssuesDon’t put up with themBlasting and peeling of coatings and antifoulHard growth and weed attractionTimber Rot or Alkaline degradation

Paint BlastingOver protection

Paint BlastingOver protectionHull antifoul blasted from bronzeskin fittings.The mV potential of zinc hasremoved the paint from all fittingsbonded to it, damaging them andleaving them exposed to growthattack.PREVENTABLE

Growth AttachmentOver protection

GrowthOver protectionA lot of hard growth on allsubmerged metal.Marine organisims are attractedto the high electrical currentgenerated by Zinc.Anodes with a lower mVpotential will not attract the samelevel of growth.PREVENTABLE

Eliminate Growth12 Months in the water with one 2.5kgMaddox anode fitted.Maximum efficiency with reduced annualoperating and maintenance costs.

Timber RotAlkaline degradationElectroplating action betweenmetals leaves an electrochemical reaction whichprovides cathodic protection.This reaction is very similar tothe production of caustic sodawhich is used to disolve timber.

Timber RotAlkaline degradationSeen here around the shaft seal ofa well known Perth wooden boat.The high potential of a zincshaft anode has destroyed thecellulose fibre in the wood.By international standards,zinc is not the recommendedanode material for a timberboat.PREVENTABLE

Bonding SystemsA typical star network

Bonding SystemsMore important than you think

Bonding SystemsA bonding system links allsubmerged metal to beprotected with each other andthe anode on the transom.The system ensures thesubmerged metals have thesame mV potential as theanode. If a connection isbroken or is of poor quality,little or no cathodic protectionis available.Almost every vessel will haveone, do you recognise yours?

Bonding Systemsbest practiceAn effective and efficient bonding system;Is connected in a star network to all submerged metal to be protected and tothe transom anode.Uses multi stranded wire which is tinned copper and green and gold insulated.Minimum 4mm, recommended 6mm & 10mm AWG.Use zinc plated copper or stainless steel ring tounge connectors with heatshrink ends.Is engineered to ensure the integrity of all connections in its network to thelowest ohms resistance possible.Is maintained by the owner or marine trade at periodic intervals to ensurecontact and performance.

Sacrificial AnodesThere are other options

Sacrificial AnodesFirst experimented with in 1824 by the Royal Navy. Iron on copper sheath.Designed to waste before the important parts of the vessel.DNV & ABYC standards state no less than -200mV and no more than -300mVdifferentialMost non metallic vessels are over protected with zinc.Zinc is recommended for protecting aluminium hulls and aluminium drive partsonly. See Galvanic Series of Metals.

Galvanic Series of MetalsANODECATHODE

Anode SelectionmV potentialKnown / accredited anode material mV potential tested independent to othermetals using an Ag/AgCl reference electrode.Metallic hulls oraluminium drive partslike stern drive,outboards and saildrives.Stainless and bronzeon fibreglass andtimber boats

RecommendedRange -mVABYC recommended range for effective cathodic protectionAs measured by an Ag/AgCl reference electrode.

Anode MaintenanceAnodes must be visually and physically inspected for connection and performanceat appropriate intervals.MPS recommend regular;testing for appropriate mV potential for your vessel.testing for sustained mV potential across the bonding network.visually inspect and physically tighten anode bolts and bonding contactsThe initial periodic performance of these tests will create its own ongoingmaintenance schedule.

MPS GuaranteeMPS guarantee that a vessel improved and repaired with respect to theseworlds best practice instructions will experience:Significantly less opportunity for corrosion or electrolysisless growth on hull and drive partsmore efficient running performanceless annual maintenance costs associated with anodes or therepair of corrosion, paint blasting and timber damage.

Who is ResponsibleMarina Operators - Australian Standards state that a marina operatormust inform members that an Electrolysis Blocker or isolationtransformer will help reduce corrosion. SYC has done this.Marine Trades – Offer the industries best practice work standard, focuson continual education, consider products and services with betterproven results.Owners – Ask more questions regarding the condition of your vesseland learn to identify preventable issues, consider preventablemaintenance solutions.

Products and ServicesMPS are manufacturers and suppliers of;High performance composite Maddox anodes.Shaft grounding solutions.Australia’s only ABYC, ASNZS and NATA approved Electrolysis Blocker.Testing and monitoring equipment.Vessel bonding design and installation.Marine corrosion specific education and training.

The future costs and condition of your vessel are in yourhands. Recurring issues once dealt with year after yearhave long been identified as preventable.What will you do about it?Presented By: Jeff BullockMarine Protection Systems Pty ltdP: 9204 3476E: info@marineprotectionsystems.com.auW: www.marineprotectionsystems.com.au

Strategies to prevent corrosion, marine growth and reduce on-going . around skin fittings. Seen here on a toilet intake that has stainless through hull, bronze gate valve and custom stainless top fitting. No bonding