Cathodic Protection Design:
Cathodic protection systems are systems which are designed to control the corrosion of a metal surface. Corrosion can destroy the integrity of your infrastructure. Patching the damaged area may seem the simplest and least expensive process of repair, but it may also be the least effective method for cathodic protection. Materials used for patching soon require repairs, and on a cyclical basis each time growing more expensive. These repairs weaken the structure and may lead to the need for total replacement.
Drop Cell Survey:
The drop cell survey is performed from the surface and requires that a reference electrode is lowered through the water column adjacent to the platform structure. Readings are recorded at predetermined depth intervals at various locations around the structure. This method is quick and inexpensive, it will give some indication of the surface potentials on the structure. They will not be accurate due to the fact that the reference electrode could be remote from the structure, however, the readings obtained do give a good general indication as to the protective status of the structure. Potentials recorded are generally optimistic so far as cathode potential is concerned; errors typically range between (-)0.02 and (-)0.06 Volts vs Ag/AgCI, depending on sea conditions, water depth and the protective level of the structure. It is fair to say that if a well conducted drop cell survey indicates marginal protective levels, then in most cases, a detailed survey would reveal areas which were below protected criteria.
The specialized inspection program is considered a baseline inspection the difference between the baseline inspection and follow up periodic inspection is that the baseline includes significant pre-inspection efforts to obtain data and drawings. It also enables the activity to update and confirm current facility construction and configuration and to establish an accurate facility documentation. The activity should submit a copy of any data obtained and this data will be recorded in a format suitable for entry into the data base. Once accurate drawings and data are on file, many of the documentation task need not be repeated in the follow up inspections so that these data will then form a true baseline for the facility. These baseline data are included in the inspection report, and will be reused in subsequent inspections of the facility.