The risk of hydrogen embrittlement in high-strength prestressing steels under cathodic protection

1993 ◽  
Vol 64 (1) ◽  
pp. 97-101 ◽  
Author(s):  
Bernd Isecke ◽  
Jürgen Mietz
Keyword(s):  
Hydrogen Embrittlement ◽  
Cathodic Protection ◽  
High Strength

Effects of Cathodic Protection on Cracking of High-Strength Pipeline Steels

2010 ◽  
Author(s):  
M. Elboujdaini ◽  
R. W. Revie ◽  
M. Attard
Keyword(s):  
Hydrogen Embrittlement ◽  
Cathodic Protection ◽  
Cathodic Polarization ◽  
Water Solution ◽  
Reference Electrode ◽  
High Strength ◽  
Point Of View ◽  
Pipeline Steels ◽  
Different Levels ◽  
Reduction Index

A comparison was made between four strength levels of pipeline steels (X-70, X80, X-100 and the X-120) from the point of view of their susceptibility to hydrogen embrittlement under cathodic protection. The main aim was to determine whether the development of higher strength materials led to greater susceptibility to hydrogen embrittlement. This was achieved by straining at 2×10−6 s−1 after cathodic charging in a simulated dilute groundwater solution (NS4) containing 5% CO2/95% N2 (pH approximately 6.7). The results showed quantitatively the loss of ductility after charging, and the loss of ductility increases with strength level of the steel. All four steels exhibited a loss of ductility at overprotected charging potential and an increasing amount of brittleness on the fracture surface. Ductility in solution was measured under four different levels of cathodic protection, ranging from no cathodic protection to 500 mV of overprotection with respect to the usually accepted criterion of −850 mV vs. Cu/CuSO4 reference electrode. Experiments were carried out by straining during cathodic polarization in a simulated dilute ground water solution (NS-4 solution). Strain rates used were 2×10−6 s−1. After failure, the fracture surfaces were characterized by examination using scanning electron microscopy (SEM). Under cathodic protection, all four steels showed loss of ductility and features of brittle fracture. The loss of ductility under cathodic polarization was larger the greater the strength of the steel and the more active (i.e., more negative) the applied potential. The Ductility Reduction Index (DRI) was defined to quantify the reduction in ductility.

Influence of pH on Hydrogen Absorption in Duplex Stainless Steel

2013 ◽  
Vol 794 ◽  
pp. 592-597
Author(s):  
V. Viswanathan ◽  
Nage Deepashri
Keyword(s):  
Stainless Steel ◽  
Hydrogen Embrittlement ◽  
Duplex Stainless Steel ◽  
Cathodic Protection ◽  
Oil And Gas ◽  
Current System ◽  
High Strength ◽  
Oil And Gas Exploration ◽  
Production Of Hydrogen ◽  
Critical Ph

With rising demands, oil and gas exploration of high-pressure high-temperature (HPHT) wells are increasing worldwide. Due to aggressiveness of HPHT environments, piping and equipments are constructed with high-strength corrosion resistant alloys (CRAs). Duplex stainless steel is one of the candidate alloys that offer high strength along with corrosion resistance. It possesses the advantages of both austenitic and ferritic stainless steels and hence, the name duplex or dual phase stainless steel. In order to control corrosion, cathodic protection is commonly being employed on the structures and equipment. Cathodic protection is accomplished by applying a direct current to the structure which causes the structure potential to change from the natural corrosion potential (Ecorr). The required cathodic protection current is supplied by sacrificial anode materials or by an impressed current system. Hydrogen embrittlement (HE) is an associated phenomenon, which results in the production of hydrogen ions, leading to its absorption in the protected metal and subsequent hydrogen embrittlement of metals and welds. To prevent this embrittlement, cathodic protection is closely studied in terms of finding the critical potential, pH, temperature etc. that does not cause hydrogen embrittlement. This paper describes the study carried out to find the role of pH on the absorption of hydrogen in Duplex Stainless steel. It has been observed that at a critical pH, hydrogen intake in the sample is very high, as compared to the pH below and above the critical pH. Critical pH observed for duplex stainless steel is a trade of between hydrogen evolution and absorption for given duplex structure.

scholarly journals Effect of Strain Rate on the Hydrogen Embrittlement Property of Ultra High-strength Low-alloy TRIP-aided Steel

2019 ◽  
Vol 105 (4) ◽  
pp. 443-451 ◽  
Author(s):  
Tomohiko Hojo ◽  
Riko Kikuchi ◽  
Hiroyuki Waki ◽  
Fumihito Nishimura ◽  
Yuko Ukai ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
High Strength

Implementation of HSLA-100 Steel in Aircraft Carrier Construction—CVN 74

1995 ◽  
Vol 11 (02) ◽  
pp. 97-101
Author(s):  
J. P. Christein ◽  
J. L. Warren
Keyword(s):  
Hydrogen Embrittlement ◽  
High Strength ◽  
High Yield ◽  
Aircraft Carrier ◽  
Implementation Plan ◽  
New Material ◽  
Welding Procedure

High strength low alloy (HSLA)-100 steel was developed to be less sensitive to hydrogen embrittlement than high yield (HY)-100 steel. The primary benefits sought through the use of this new steel were savings in energy, labor, and scheduling that would result from reduced preheat for welding. This paper reviews the overall efforts required to implement the use of HSLA-100 steel during CVN 74 aircraft carrier construction. It discusses the engineering and design effort required to incorporate a new material on a vessel midway through construction. Also included is a discussion of the development of an implementation plan which ensures successful welding procedure qualification, production welding, and inspection of HSLA-100 welds. Results confirm that HSLA-100 steel can be successfully substituted for HV-100 steel in a shipyard environment, and that significant benefits can be realized from reduced welding preheat. Also, key elements of future applications of HSLA-100 are presented.

New Method for In-Trench Pipeline Support

2012 ◽  
Author(s):  
Geoff W. Connors
Keyword(s):  
Cathodic Protection ◽  
Welding Process ◽  
High Strength ◽  
Test Water ◽  
Poly Type ◽  
Additional Protection ◽  
Injection Molded ◽  
Heavy Loads ◽  
Sand Piles

Protection of the pipe during and after pipeline construction is of paramount importance for safety and pipeline integrity. Areas of rock and stone are often encountered during construction of new pipelines. Even with modern pipeline coatings, additional protection for the pipe is necessary where rock or stone exposure is significant. Historically, additional pipe protection used in these types of situations is achieved through adding either a significant layer of sand or select backfill above and below the pipeline (sand padding) and/or by attaching a high-impact resistant, poly-type rock shield around the pipeline during the pipeline installation process. To accommodate sand padding, some form of intermittent support of the pipeline is generally required to elevate the pipeline off the trench bottom. Similar intermittent support is also recommended practice when using poly-type rock shields to keep the pipeline from fully resting on trench rocks. Current methods of in-trench support involve sand piles, sand bags, spray foam and individually formed foam pillows — each with drawbacks: i) Sand Piles are difficult to install and often oval or dent the pipe when improperly placed. ii) Sand bags require hand placement for proper support. In open trenches, this can be time consuming and unsafe. Improper placement can cause the pipe to oval or dent. iii) Spray-in foam is considered to be an obstruction of cathodic protection currents. Newly constructed pipelines full of hydrostatic test water and one metre cover can cause foam to compress excessively. iv) Foam pillows are light and easily placed — but can float out of position and compress or crack under heavy loads. As with all foam, cathodic shielding is always a concern. A new, engineered method of in-trench pipeline support is now available — the Structured Pipeline Pillow (SPP). SPP’s are injection molded and made from high strength, environmentally inert polypropylene or polyethylene resins. Designed to support any size pipeline, SPP’s are most effective with larger diameter, heavier pipelines. One SPP is engineered to carry a single 40′ joint of heavy wall pipeline filled with hydrostatic test water. Compared with current methods, SPP’s: i) Stack tightly for transport. ii) Are light enough for installation from outside the trench and resist floatation when ground water is present. iii) Help ensure the pipeline is centered in the trench during the pipeline installation. iv) Maintain long-term pipe clearance above rocky trench bottoms. v) Ovality and denting concerns are reduced. vi) Allow cathodic protection an easy path to the pipeline. vii) Will never biodegrade. In their extended stacking mode, SPP’s tested well as an effective alternative to wooden skids for many situations such as pipe stockpiling; stringing along the rights-of-way (ROW); and even for some low level skidding during the welding process.

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