Roy Johnsen | Norwegian University of Science and Technology (original) (raw)

Papers by Roy Johnsen

Elsevier eBooks, 2007

Publisher Summary This chapter discusses experience with the use of copper alloys in seawater sys... more Publisher Summary This chapter discusses experience with the use of copper alloys in seawater systems on the Norwegian Continental Shelf (NCS). It presents that the history of oil exploration on the NCS goes back to the 1970s. The first commercial fields put in operation were the Ekofisk and the Statfjord Fields, both of which were operated by American oil companies – Phillips Petroleum and Mobil. Due to the lack of people with experience in oil and gas production in Norway at that time, the operating companies brought people from the United States to design and manage the operation of the installations. They used their well-established onshore experience regarding both design and material selection. Seawater is among the most corrosive environments in connection with oil and gas production. For seawater systems, the original solution was carbon steel with or without internal concrete. The chapter presents an example of the preferred seawater material for some main offshore installations on the NCS. It also draws some conclusions for operators on the NCS: (1) The CuNi alloys have been used for seawater handling systems by the oil companies, (2) Field experience has shown serious corrosion and/or flow-induced corrosion problems; often due to operation outside of acceptable parameter windows, including galvanic couplings, and (3) The CuNi alloys will have a limited market as piping material in seawater systems on the NCS in the future.

Corrosion, 2010

This paper describes a risk-based maintenance management system for protective coatings and how i... more This paper describes a risk-based maintenance management system for protective coatings and how it might influence offshore maintenance processes. Maintenance of protective coatings is one of the more resource-demanding and, hence, costly operations on offshore installations. On older platforms, typically about 5% of all man-hours are related to coating maintenance (including scaffolding). The cost is strongly influenced by initial coating system selection and maintenance strategy, together with the required lifetime. A new, risk-based maintenance management system is being developed, and Part 1 of this series discussed the risk analysis methodology. Parameters influencing the risk related to coating maintenance have been identified, and a framework for control and monitoring of these parameters has been established. This framework aims to optimize maintenance and inspection programs through risk evaluations, and may affect:-inspection methodology and intervals,-priority-assignment during maintenance,-coating selection, and-follow-up of suppliers and contractors.

Corrosion, Mar 26, 2017

Effect of microstructure on corrosion resistance and heat resistance of flame-resistant Ca-added ... more Effect of microstructure on corrosion resistance and heat resistance of flame-resistant Ca-added magnesium alloy AZ61 (AZX612) were investigated. An extruded and twin-rolled casting magnesium alloys AZX612 were used with a view to better understanding the relationship between microstructure and these properties. The microstructures of the magnesium alloys were characterized by optical microscope (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS). The shapes of compounds in the alloys observed by EDS were significantly different; spherical distribution in grain for the extruded magnesium alloy and preferential formation on grain boundaries for the twin-rolled casting magnesium alloy. The different microstructure of the two alloys resulted in showing the different properties. Immersion test in 5 mass% NaCl aqueous solution revealed that the corrosion rates for the extruded and twin-rolled casting magnesium alloys AZX612 were estimated to be 6.5 and 15.0 mm/year, respectively, indicating that the corrosion resistance of the extruded magnesium alloys AZX612 were more superior than that of the twin-rolled casting one. On the contrary, the heat resistance of the alloy did not change depending on the microstructure.

Corrosion, 2000

This paper presents a new technology for inspection and monitoring of metallic objects, pipes and... more This paper presents a new technology for inspection and monitoring of metallic objects, pipes and vessels. The system is based on a field proven, non-intrusive, internal corrosion monitoring technique, which is designed to detect and quantify general metal loss, cracking, or pitting due to corrosion or erosion. The inspection tool allows inspection in areas where more conventional inspection techniques (ultrasonic or intrusive probes) are either costly or difficult to apply. The significant advantages include the ability to operate in a wide temperature range (-40° to + 400°C); non-intrusive, no operator dependency; measures changes in the actual pipe wall, allows remote intervention; can be applied to any geometry or wall thickness and maintains a high sensitivity of one part per thousand of wall thickness for general corrosion. This paper describes the inspection system and results from a validation test performed to prove the quality of the measured data for weld root corrosion.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Dec 1, 2022

Wear, Sep 1, 2013

Galvanic coupling during tribocorrosion of passive metals at open circuit potential (OCP) generat... more Galvanic coupling during tribocorrosion of passive metals at open circuit potential (OCP) generates a wear accelerated corrosion process within the depassivated area (worn surface) that is electrically in contact with the still passive one. The galvanic coupling effect at OCP was recently modelled using an electrochemical approach allowing for the theoretical quantification of the wearaccelerated corrosion under equilibrium conditions. Despite the usefulness of this model that mathematically determines the electrochemical conditions inside the wear track in terms of anode potential via the approximation of the net anodic current density, an experimental technique allowing for their experimental determination is essential in the effort to verify the galvanic coupling models and further understand the tribocorrosion mechanisms at OCP. In the present work, a new experimental technique based on galvanic current and potential measurements through a Zero-Resistance Ammeter (ZRA) for quantifying the electrode potential and anodic current inside the wear track during rubbing at OCP has been assessed. This experimental setup has allowed for the first time to determine the prevailing electrochemical conditions (electrode potential and anodic current) inside the wear track by solely exposing the wear track to the electrolyte and physically separating the cathode from the anode (wear track). The effects of sliding wear at open circuit potential have been investigated for a super duplex stainless steel (UNS S32750) in 3.4 wt.% NaCl. The new experimental setup proposed in this work, separates the cathode from the anode and exposes solely the wear track to the electrolyte. Using well-established electrochemical theories, the effect of the extent of the galvanic coupling on wear at the open circuit potential conditions has been quantified. WEAR Confirmation of Authorship Please save a copy of this MS Word file, complete and upload as the "Confirmation of Authorship" file. As corresponding author, I Nuria Espallargas hereby confirm on behalf of all authors that: 1) The authors have obtained the necessary authority for publication. 2) The paper has not been published previously, that it is not under consideration for publication elsewhere, and that if accepted it will not be published elsewhere in the same form, in English or in any other language, without the written consent of the publisher. 3) The paper does not contain material which has been published previously, by the current authors or by others, of which the source is not explicitly cited in the paper. Upon acceptance of an article by the journal, the author(s) will be asked to transfer the copyright of the article to the publisher. This transfer will ensure the widest possible dissemination of information. Confirmation of Authorship Click here to download Confirmation of Authorship: authorhip confirmation.doc

Journal of Materials Science & Technology, Feb 1, 2023

CRC Press eBooks, Jun 21, 2007

Corrosion, Mar 11, 2007

Current requirement and calcareous scale properties on carbon steel were investigated as a functi... more Current requirement and calcareous scale properties on carbon steel were investigated as a function of applied potential, fl ow rate, and time in natural seawater. The current requirement was dominated by oxygen reduction during the initial stage of polarization after application of cathodic protection. However, as the calcareous scale deposited, oxygen reduction reaction rate decreased and hydrogen evolution became the dominating cathodic process. Furthermore, the rate of hydrogen evolution appeared to become catalyzed by the presence of the calcareous scale deposit. At a given fl ow rate, a maximum was obtained when the Ca/Mg ratio measured in the calcareous deposit was plotted as a function of applied potential. The maximum became larger and shifted to more active potentials with increasing fl ow rate, as determined by the pH and potential-dependent competing kinetics of calcium hydroxide (Ca[OH] 2) and magnesium hydroxide (Mg[OH] 2) deposition. The applied potential giving the maximum Ca/Mg ratio in the calcareous deposit provided the best protection and minimum current requirement at a given fl ow rate.