Page 183 - Introduction to Naval Architecture

STRENGTH

0 10 20
Age of ship (t, years)
Figure 7.22 Corrosion rates (courtesy RINA)

naturally anodic area. The potential is measured against a standard
reference electrode in the water. Typical current densities required to
2
2
be effective are 32mA/m for painted steel and 110mA/m for bare
steel, but they vary with water salinity and temperature as well as the
ship's speed and condition of the hull. The system can be used to
protect the inner surfaces of large liquid cargo tanks.
Monitoring off-line loads on the main hull at sea is now fairly routine
with stress monitoring systems fitted to a number of bulk carriers.
These systems are being developed to give the Master warning of
impending structural problems and to include on-line corrosion
monitoring.

STRUCTURAL SAFETY

Various modes of failure were outlined early on. A designer must
evaluate the probability of failure and reduce its likelihood. First a