1. Introduction
This manual gives instructions for operating the Seaguard Digital
Corrosion Tester to test boats and other marine structures in
seawater. The professional model is designed to be used by
marina operators, shipyard workers and service technicians with
silver / silver chloride reference cell (SSC).
Measuring corrosion
Vessels in seawater produce galvanic reactions just like an electric
battery does. Electrical current will flow through the hull when the
hull contains different metals. This happens even in wooden hulls
with motors attached. The most active metal discharges electrical
current to the other metal, cycling the current back through the
seawater. The most active metal becomes corroded.
If a metal part is greater than 0.2 volts negative to its natural
potential, it will not corrode. If the part is positive to its natural
potential then we know that it is connected to a different type of
metal and it will cause corrosion.
One of the most effective protection methods is to add sacrificial
electrodes called anodes to make the hull become a cathode,
where the current flows from one to the other.
To measure the actual corrosion process we measure the
electrical potential of the hull. If the voltage reading is too high, it
means the hull is not protected. If the voltage is too low, we say it
is “over-protected.” Over-protection will cause the hull coating to
lose its bond to the hull and peel off (“disbondment”). So checking
the electrical potential is very important.
The Seaguard Digital Corrosion Tester is a high-impedance
voltage meter with a reference cell. The tester is specially designed
to check the electrical potential of the hull at different locations on
the hull while the boat is in seawater. Each reading is color coded
to indicate whether the boat is protected (PASS, green), under-
protected (FAIL, red), or overprotected (OVER, yellow).
The following parts are included:
• Corrosion tester handheld device
• Ag/AgCl reference cell (SSC) with 20 feet long cable (Pro Model)
• Test probe with alligator clip and 6 feet long cable
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