Prestressed concrete cylinder pipe pipeline sections projected to exhibit wire breaks were detected - and one not so - were excavated, removed, inspected, and dissected. Corrosion had initiated upon the inner surface of shorting straps and spread to the prestressing wires. A mechanism for this corrosion is presented and the findings discussed.
Chloride induced corrosion is recognized as a significant disease in the nation's concrete infrastructure. This paper will provide an overview of the various corrosion mitigation techniques available and then focus on two innovative methods of using discrete anodes embedded within the concrete to provide corrosion protection to existing structures.
Solvent-based acrylic carbon paint anodes were installed on the north approach spans of the Yaquina Bay Bridge (Newport OR) in 1985 and performed well after 15 years. Anodes were inexpensive and repairs easy. Depolarization potentials are consistently above 100 with long-term current densities around 2 mA/m 2. Bond strength remains adequate.
Potential attenuation equation for pipelines and risers with multiple, equally spaced, identical superimposed spherical (bracelet) galvanic anodes that incorporates all relevant resistance terms (anode, coating, polarization, and metallic return path) has been modified for situations where anodes are displaced.
Several well casings were selected as candidates for down hole inspection logs to determine if cathodic protection could be a solution to the external corrosion problem. "Test" cathodic protection systems were installed. Based on logging results and economic evaluation, implementation of a cathodic protection pilot project commenced.
A simulation software for the cathodic protection (CP) of underground pipeline networks is presented. In this paper, the software will be applied to two different cases. The first concerns the design of the cathodic protection of a 55 km pipeline section. The second is the evaluation of an existing pipeline network in the north-west of The Netherlands.
SINTEF (a Norwegian research Co.) made studies of the sensitivity to hydrogen embrittlement (HE) of super 13Cr martensitic stainless steels. These tests are summarised in this paper. Both slow strain rate (SSR), 4-point-bend and fracture mechanics testing have been conducted. The effect of temperature, cathodic protection (CP), applied potential, strain rate and H2S were investigated.
Telluric currents cause variations in pipe-to-soil potentials that take the potentials outside the desired range for cathodic protection. This paper reviews the causes of telluric currents, such as geomagnetic storms and tidal water movements, and shows how knowledge of these phenomena can be used to determine the occurrence of telluric current in pipelines.
Laboratory testing to qualify several materials for high strength fastener applications for two projects has shown that, in the presence of cathodic protection, nickel alloys 718 and 725 offer the best resistance to hydrogen embrittlement and are available in the strength/size required for high pressure and moderate temperature applications for sub-sea applications.