Galvanic corrosion on boats
August 16, 2020
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Saturday, July 3, 1999. The “Random Harvest”, a 33-foot GRP charter boat, departs from her home port of Brighton with a crew of 2 and
Information on the order
Purchase appraisal for an aluminum sailing yacht “Van Dam Nordia 54” in Italy.
Scope of order: Standard inspection including test drive, thermographic inspection of the machine system and inspection of the cathodic protection (hull potential).
Data
VAN DAM
Nordia 54
Nordia 54
- Length: 16,40m
- Width: 4,50m
- Material: Aluminum
- 1x90kW Perkins
Measurement of the trunk potential
With an aluminum yacht in particular, it is especially important to make sure that the cathodic protection is also working properly and that there are no undesirable galvanic or electrolytic voltages that could lead to significant corrosion problems.
To check this, we measure the voltage potential of the hull against a“reference electrode” made of a special silver/silver chloride material mix, which is also used as a reference point for many electrochemical analyses.
This so-called “hull potential” is then compared with relevant comparative tables, which makes it possible to assess whether there is sufficient cathodic protection for the materials used in the area of the hull.
As was to be expected, however, the naval architects at Van Dam did their homework here.
In addition, the previous owner had installed high-quality Trudesign plastic seacocks, which further minimized the risk of galvanic reactions.
SEA TRIALS
The absolute highlight of every inspection is, of course, the sea trials.
Especially when the sun is shining and the Mediterranean is at its best.
Category A defects
2
Category B Defects
5
Category C Defects
7
Defects categories
To assess the significance of the defects found and thus their repair priority, they are divided into the following categories:
Category A
Defects that acutely endanger or impair seaworthiness, functionality, navigational safety and/or the safety and health of persons on board and require immediate rectification.
Category B
Defects that do not pose an acute safety threat or merely restrict comfort on board and therefore have a lower priority for rectification.
However, it may be necessary to monitor developments.
Category C
Defects that do not pose a safety threat and are predominantly cosmetic and therefore do not have repair priority.
However, the value may be impaired.
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The right cathodic protection for boats and yachts
August 15, 2020
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As we have known at least since reading the article“Galvanic corrosion on boats“, the right protection against galvanic or electrolytic corrosion is a critical measure