BATTLING CORROSION ABOARD SHIPS - Part 3

Strategies for Prevention

Preventive measures will decrease maintenance costs, early system failures, and an overall improve service life of ships granted they are detected in enough time.

a. Modifying the Corrosive Environment

Hence, Inhibitors are salt water or electrolyte solutions which are controlled. Anodic inhibitors migrate to the anode creating a protective barrier which as a result, stops corrosion in its tracks. Therefore, Cathodic Inhibitors migrate to the cathode which prevents the absorption of oxygen or hydrogen.

In addition, Cathodic protection uses sacrificial metal to act as the anode which creates a protective barrier. This metal deteriorates first instead of the ships protected layers.

For example on the hull of a ship, zinc plates prevent corrosion of any sub-surfaces.

b. Protecting the Corrosive Environment

As a result, in the hope of protecting the vessel coat it with three different paint solutions.

Binders – Therefore, the binder is a film forming component of paint.

Pigments/Extenders – these powders mix with the binder at various particle sizes and enhance the overall effectiveness of the binders.

Solvents -Eventually evaporate from the surface and help for easy application.

In conclusion, it is important to have the proper plating before the equipment is put to work. As a result the equipment will last longer and will become resistant to the elements.

Battling Corrosion aboard Ships - Part 2

Impressed current cathodic protection (ICCP) systems are the ultimate state-of-the-art, long-term solution to corrosion problems, and are recognized as a superior alternative to sacrificial anode systems, which require frequent replacement. Impressed current cathodic protection systems are preferred by ship owners because they reduce fuel cost and maintenance.

ICCP systems work by supplying a controlled amount of DC current to submerged surfaces using highly reliable mixed metal oxide anodes and zinc reference electrodes. This electrical current, constantly monitored and regulated by the system itself to prevent the electrochemical action of galvanic corrosion before it begins.

For more than 25 years, sea-going vessels of every type and size – oil tankers, LNG carriers, cruise ships, pleasure craft, workboats, semi-submersibles, and more – have benefited from the 24-hour protection provided by Impressed current cathodic protection systems against the costly, corrosive effects of electrolysis.

Reference Cell / Electrode
ICCP systems are controlled to assure optimum protection. This control is obtained by inserting a third electrode between the anode and the cathode. The third cell/electrode is insulated and does not receive any anode current. This cell/electrode is freely corroding and it becomes the starting point — or reference — in eliminating corrosion. Cell/Electrodes constructed of Zinc are used exclusively with the ICCP system.

Zinc Reference Electrode

Power Supply Unit / Control Panel
Each standard ICCP system utilizes a solid-state controller which monitors and controls the protection as measured by the Zinc Reference electrode. Anode current automatically increases when the electrode potential falls below the designated control value. An over- and under-potential alarm is provided with the system package. We also offer optional digital control, state-of-the-art technology with every system. The computer controller (shown below is more accurate and provides central control, monitoring, data storage and hard printout.

Mixed Metal Oxide Anodes
Mixed Metal Oxide anodes of are used exclusively for ICCP systems. ICCP anodes are manufactured in Linear Loop , Elliptical and Circular designs with insulating holders. They are available in a single unit capacity of 75 to 225 amperes, as required for various installations.

Impressed Current Corrosion Protection System – MMO-TI Linear Strip Anode– MMO-TI Disk Anode

System Advantage

·         Increased life of rudders, shafts, struts and propellers as well as any other underwater parts affected by electrolysis

·         Anodes are light, sturdy and compact for easy shipping, storage and installation

·         Anodes, reference cells and automatic control systems maintain just the right amount of protection for underwater hulls and fittings, unlike standard zinc anodes, which can’t adjust to changes in salinity or compensate for extreme paint loss

·         Automatic control equipment ensures reliable, simple operation

·         Optimum documented corrosion protection at minimum overall cost

·         Only one installation required for the life of the vessel or structure

·         Increased dry-dock interval