Understanding Sacrificial Anodes on Ship

3/20/14 Understanding Sacrificial Anodes on Ship

www.marineinsight.com/marine/understanding-sacrificial-anodes-on-ships/ 1/13

1 COMMENT

Share on Facebook

Understanding Sacrificial Anodes on ShipsNOVEMBER 21, 2010 BY ANISH

Tweet 3 1

Corrosion is one of the greatest enemies of the ship and its machinery. It is also

the toughest enemy to fight against for the people working on the ship. Iron is

one substance which is used in abundance on the ship. From the main body of the ship to the smallest

equipment used in operations, iron makes its presence felt in almost every type of equipment used on

board the ship.

Premium eBook Store Marine Engineering Nautical Science Infographics Maritime Links

Send Us News Advertise Resources Team

HOME NEWS TECHNOLOGY NAVIGATION SAFETY CAREERS

LIFE AT SEA PIRACY VIDEOS EBOOKS

15Like



A ship is continuously in contact with water and moisture laden winds which makes it highly

susceptible to corrosion. The other body of the ship (mainly hull) is continuously in contact with water,

making it extremely vulnerable to corrosion. It is for this reason sacrificial anodes are used to protect

the parent material. In this article we will have a look at the working of sacrificial anodes on ship.

It is to note that the sacrificial anodes which are protecting the parent material should lie higher in the

electromotive series or galvanic series of metals.

How Sacrificial Anodes Work?

VGP Wire RopeLubricantrocol.com/biogen

If your vessel enters U.S. coastal waters you

now need a VGP lubricant



Sacrificial anodes works on the principle similar to electrolysis, according to which if an anode and a

metallic strip are dipped in electrolytic solution, anode electron will dissolve and deposit over the

metallic strip and make it cathode.

In the case of a ship, sea water acts as an electrolyte and transfers the electrons from the anode by

oxidizing it over the steel plate and making a protecting layer. If the metal is more active it will be

easily oxidized and will protect the metallic compound by making it act as cathode. The anode will

corrode first sacrificing itself for the other compound and it is thus called sacrificial anode.

Electromotive series or galvanic series metals

Anode materials

Magnesium(Mg)

Aluminium(Al)

Zinc (Zn)

Chromium(Cr)

Iron(Fe)

Nickel(Ni)

It can be seen from the table that for protecting iron any material above in the series are useful. These



metals are preferred because they are easy and cheap to replace the anodes rather than complete a

large sheet of metal.

These anodes are used in various applications such as :

1) Protecting the ships hull.

2) Protecting the ballast tanks corrosion.

3) Protecting the heat exchangers.

4) Sea chests

The most common metals used for sacrificial anode is zinc.

Frequency for Changing of Anodes

The frequency for changing of anodes depends on the application where the anodes have been used.

In case the anodes are attached to the ships hull, then they are to be checked during dry dock which

takes place after 2 to 3 years. If the anodes are found completely corroded then anodes of bigger size

should be fitted, for fully corroded means that the material used was of poor quality or a large amount

of material is required to protect the hull. Generally, sacrificial anodes are changed at every dry dock.

If sacrificial anodes are used for heat exchangers and it is found during inspection that the anode left



is only 10% then also it has to be changed.

How to Assess if the Anodes are Working Properly or Not?

During the inspection of heat exchangers or sea chest, if the condition of anode is same as it was

installed then it indicates that the sacrificial anodes are ineffective.

The main reason for this is that the electrical continuity between the parent materials is not made.

Because of this the parent metal starts getting corroded instead of the anodes. It is therefore

important to check the electrical continuity during installation.

If you liked this article, you may also like to read What is Marine growth preventive system (MGPS) ?

Image Credit

Amteccorrosion

Rustyiron

Shipyard, NodosaShipyardnodosa.com

Shipbuilding and Shiprepair Tug, Dredger,

Fishing vessel, etc.



Related Posts

Get Free News Updates Daily

Sign-up below for more News, Articles, and Offers Submitted Directly to Your Inbox

Enter your email

GET ACCESS TODAY!

About Anish

An ardent sailor and a techie, Anish Wankhede has voyaged on a number of ships as a

marine engineer officer. He loves multitasking, networking, and troubleshooting. He is the

one behind the unique creativity and aesthetics at Marine Insight.

COMMENTS

Dry Dock, Types

of Dry Docks &

Requirements for

Dry Dock

Procedure for

Cleaning Fuel Oil

Tanks on a Ship

Procedure for

Starting and

Stopping of

Sewage

Treatment Plant

on a Ship

How are Piston

Rings Made?

Little Known Way

to Save Hundreds

of Dollars on

Vacation Resorts

(9nl.com)

How To Clean

Hardwood Floors

(Shaw)



saytan says

October 24, 2013 at 3:39 am

Hi Anish I am a marine student and at the moment in the final year. My project is on hull

thickness testing near the sacrificial anode. Is is possible for you to post more information

about this subject. It would be of great help for me.

Regards,

Saytan

LEAVE A REPLY

Name *

Email *

Website

Comment



POST COMMENT

EXPERT AUTHORS

Anish Wankhede, 2nd Engineer

View My Blog Posts

Pankaj Bhargava, Master Mariner

View My Blog Posts

Abhishek Bhanawat, Chief Officer



View My Blog Posts

Bikram Singh, Chief Officer

View My Blog Posts

Amitava Chakrabarty, Marine Pilot

View My Blog Posts

Mohit Sanguri, Chief Engineer

View My Blog Posts

Raunek Kantharia, Maritime Writer

View My Blog Posts

SEARCH MARINE INSIGHT

SEARCH



SUPPORT US BY DONATING A LIKE

161,758 people like this. Sign Up to see what

your friends like.Like

Marine Ship Engine

Sacrificial Anodes

Ship Ships



LATEST NEWS

Rolls-Royce To Power Asias FirstGas Powered Tug

GSF Calls On Regulators ToInvestigate Impact Of P3 Proposal

Ships Requested To Keep A Look OutFor Signs Of The Missing MalaysianAirliner

Free PDF Nautical Charts NowAvailable

Wrtsil To Deliver Its Patented VIECSeparation Technology For ThreeNorth Sea Oilfields

DNV GL Reduces The Impact OfVariations In Ship Construction

Siemens Showcases Shipyard Designand Production Software at APM, 2014Read More News..



NAVIGATION

What is Mediterranean Mooring ofShips?

How Baltic Mooring of Ship is Done?

How Dredging Anchor is Used forManeuvering Ships?Read more articles on navigation..

PIRACY

10 Things to Consider Before YourShip Enters Piracy Prone Area

The Menace of Maritime Piracy andSomali Pirates Is There a Solution?

Top 5 Must-Watch Somali PiratesMoviesRead more articles on piracy..

SAFETY AT SEA

10 Things Seafarers Must RememberBefore Signing Off From Ship

10 Situations Wherein Engine andDeck Officers Must Maintain EfficientCommunication

10 Important Points For ShipsMooring Equipment MaintenanceRead more articles on safety..

MARINE TECHNOLOGY

10 Practical Tips for SmoothOperation of Electronic MarineEngines



10 Electrical Jobs Marine EngineersMust Know On Board Ships

8 Ways to Monitor and MeasureMarine Engine PerformanceRead more technology articles..

Copyright 2013 MarineInsight All Rights Reserved Privacy Policy | Contact | Disclaimer | About Us

Understanding Sacrificial Anodes on Ship

Documents

Transcript of Understanding Sacrificial Anodes on Ship