Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.
CATHODIC PROTECTION FIGURE 5
Corrosion Assessment and CP Design for a Large Dry Dock in the Gulf of Mexico
A three-dimensional model of (a) the dolphin and (b) potential distribution according to a three-dimensional simulation of the system.
FIGURE 6
(a) A damaged anode and (b) the articulated design of the anode support. the water and 1,036 m2 are buried. The
corrosion of the piles is controlled by a 12 V/80 A ICCP system. Four platinized titanium anodes, 1.5-m long, are sus- pended under the dolphin. The anodes are evenly distributed among the piles. Computer simulations of the system showed that the anode distribution was appropriate. The principal problem with the system was the anode integrity. Float- ing debris periodically damaged one or more anodes. This has caused the system to be out of order for long time periods. The proposed solution was to replace
\PM ÅJMZOTI[[ IVWLM []XXWZ\[ _Q\P IZ\QK]- lated reinforced nylon bars that can bend _PMV ÆWI\QVO LMJZQ[ Q[ XI[[QVO Ja
Conclusions Highly complicated structures such as
a dry dock require the use of advanced numerical modeling to design adequate CP. Traditional design leaves vital struc- tures without protection, such as structures TaQVO JMVMI\P \PM WKMIV ÆWWZ IVL QV\MZVIT faces of the sheet piling. Accidents in the past have shown the importance of critical elements such as a watertight lock gate. Its protection has required the input of cor- rosion specialists from several disciplines. Anode support, monitoring, and connec- \QWV[ ZMY]QZM [XMKQIT LM[QOV[ \PI\ N]TÅTT \PM unique technology requirements of corro- sion control systems in a dry dock. For the buried and submerged steel
surfaces, CP is the best solution to mitigate corrosion deterioration. Most of the steel
structures are not accessible for repainting or replacement. The combination of dis- tributed anodes in submerged surfaces and remote anodes for buried structures are intended to provide adequate protection. 5IVa KITK]TI\QWV[ IVL ÅMTL \M[\[ _QTT JM necessary to avoid possible interference with other structures such as pipelines be- cause of the increased amount of current proposed in the CP design. The coating system proposed for the
internal walls of the dry dock is capable of ÅTTQVO \PM OIX[ JM\_MMV MIKP [\MMT [PMM\ and has very good mechanical resistance to the sandblasting used during ship mainte- nance. The coating application will be done after pitting repairs, which includes welding steel sheets in areas where low metal thick- ness was detected.
NACE International, Vol. 51, No. 3