Stress corrosion cracking (SCC) of carbon steel in fuel ethanol service has been observed in an increasing number of failures in the last few years. In the presence of oxygen, all of the samples evaluated in this study produced varying degrees of SCC, except for one of the producer ethanol samples. The reason for the high corrosion potential in this sample is still unknown and more detailed analysis of the sample chemical make-up is needed.
The motivation for this work was to perform a comprehensive test program to investigate several commercially available composite repair systems and their interactions with cathodic protection. Multiple test methods were utilized to prove there remains a low probability of shielding for composites of typical thickness and in a typical environment. This work will also discuss how results from current industry qualification tests (such as those specified in ASME PCC-2) can be considered when making long-term decisions regarding the effects of cathodic protection on composite repairs and the pipelines on which they are installed. This paper provides an innovative approach to test and validate the interactions of cathodic protection with several commercially available composite repair systems.
The External Corrosion Direct Assessment (ECDA) is formally listed as an acceptable integrity assessment method within Subpart O, Part 192 of the code of federal regulations regarding gas transmission pipeline integrity management2. It is a 4 step continuous improvement process to identify and address locations where external corrosion activity has occurred, is occurring or may occur1. In the pre-assessment phase, a comprehensive right-of-way inspection is performed, and pipeline operability data is collected to verify the feasibility of conducting a full ECDA for the pipeline under evaluation. In the indirect inspection phase, the status of cathodic protection and pipeline coating is tested using methods such as Close Interval Potential Surveys (CIPS) and Direct Current Voltage Gradient (DCVG) surveys.
In Upstream, CRAs (Corrosion Resistant Alloys) are widely selected to handle seawater and brines in piping, valves, pumps, heat exchangers, vessels, and seawater injection1-4. Also, disposal of produced water is commonly performed through injection into spent fields. Water from a variety of sources including produced water, seawater and surface/fresh water may also be injected to create pressure drive for existing fields. Usually dissolved oxygen (DO) is not fully controlled when there are multiple sources of injection water and sometimes even possibility of injection of fully oxygenated water exists. For oxygenated seawater, the PREN (Pitting Resistance Equivalent Number = %Cr + 3.3 *(%Mo + 0.5 %W) + 16 %N) shall be >40 and limits are applied to the temperature4. Other applications involve Solid CRA or cladded production pipelines which may get flooded with seawater during installation and precommissioning.