Steel--Testing

The efficiency of cathodic protection of steel in seawater
is partially due to calcareous deposits. To better understand
deposits, expericents are conducted testing the effects of variables
such as tecperature, velocity, and applied current, on
film formation and protection capabilities. It is the intent
of this thesis to investigate differences in using recirculating
seawater rather than once-through seawater in these experiments.
It is believed that these differences were caused by an increase
in dissolved organics in the recirculating bath. Data is in
the form of current needed to maintain a potential of -1.0v SCE
since differences in current help describe differences in film
properties.

Reverse bend, constant deflection fatigue experiments
were conducted in natural sea water at 1850 cycles per minute
(cpm) to investigate the response of 1018 notched steel to
concurrent cyclic loading and cathodic polarization. For
comparison purposes S-log N curves were also determined in
air and high purity argon. These indicate that the endurance
limit established in sea water by cathodic polarization at
-0.85 volts, Saturated Calomel Electrode (SCE), is greater
than in either air or argon. Two mechanisms are considered as
responsible for this behavior.
1. Presence of carbonate and hydroxide deposits
coupled with increased alkalinity at non-propagating
crack tips.
2. Adsorbed OH- layer at non-propagating crack tips.