This paper will consider the performance and relevance to static situations of the key types of Cathodic dip painting (CDP) Antifoulings (Rosin Modified types), the current tin free polishing types (typically acrylates of various types), and low energy surface types. Both field experience and laboratory work will be considered.
Numerous studies and papers have addressed the need and technical merits of various external corrosion protection scenarios for ductile iron pipe. Most recently, a Design Decision Model was developed to select the optimum method of corrosion protection, considering both the likelihood and consequence of failure.
In the present paper, characteristics of the AC corrosion problem are demonstrated using laboratory results and field measurements as examples. Evidence has been given that the AC corrosion mechanisms involve alkalization of the environment nearby the coating defect, and in combination with AC, corrosion may be induced.
The tendency of pipeline girth weld coatings to shield cathodic protection (CP) current was studied in the laboratory. Epoxy, epoxypolyurethane, polyurethane, and wax were investigated. Results showed that the liquid coatings, when applied extra thin to accelerate the kinetics of absorption and current transmission, all disbonded by blistering, and all allowed CP current to be transmitted.
The research described in this paper was carried out with the objective of establishing any correlation between coating performance and the results of cathodic disbondment testing. Experiments were carried out using 13 coatings. Nine samples of each coating were studied in a total of 117 experiments.
This paper reviews the concerns of applying excessive levels of cathodic protection current to pipelines and the need for establishing an upper potential limit. Coating disbondment, hydrogen induced stress cracks, stress corrosion cracking, hard spots and the problems associated with measurement of a true polarized pipe-to-electrolyte potential are addressed.
The transport of dissolved O2, and that of dissolved carbon dioxide (CO2) if present, into the disbonded region through holiday can be key to determining the disbonded corrosion rate. The evolution of chemistry in the disbonded region and the transient behavior of corrosion potential and rate in the disbonded region are investigated and reported in this work.
Results of laboratory testing of a new technology for mitigating galvanic corrosion. Incorporated into a device, referred to as the galvanic corrosion inhibiting coupling (GCIC) or bi-electrode device (BED), it creates an ohmic potential drop within the pipe and minimizes the polarization of the dissimilar metals.