Severe Marine Environment Research Articles

Passivation and Pitting Corrosion Behavior of a Novel Alloy Steel (00Cr10MoV) in Simulated Concrete Pore Solution

AbstractIn order to prolong the service life of reinforced concrete structures in a severe marine environment, a novel alloy steel (00Cr10MoV) was developed. The passivation behavior of 00Cr10MoV s...

The Attenuation of Galvanic Corrosion between Mechanically-Coupled Aluminum and Carbon-Fiber Reinforced Polymer Matrix Composites in Outdoor Environments

The effect of hydrophobic coatings on insulative skirts to attenuate galvanic corrosion between mechanically-fastened 6061-T6 aluminum (Al) alloy and carbon-fiber reinforced polymer-matrix composites (CFR PMC) was studied in outdoor environments. The utilization of hydrophobic coatings on the insulative skirt can help to attenuate galvanic corrosion by disrupting the formation of a continuous electrolyte film. Our recent work* (Srinivasan et.al. 2016) showed a novel approach of utilizing hydrophobic coatings on insulative skirts (ranging from 0 inch to 8 inch in length) to mitigate galvanic corrosion between Al alloy and CFR PMC couples in laboratory humidity chamber corrosion tests (90% relative humidity (RH) and 30°C). Shorter skirt lengths (i.e., 0.25 inch) with a hydrophobic Siloxel TM coating was shown to be most effective in attenuating galvanic corrosion based on the capillary effect that wicked away large water droplets, generated from a mechanical sprayer. During outdoor exposures, airborne salt particles are on the order of a few microns, and hence, may settled on the skirts as a relatively uniform distribution. To study the effectiveness (due to capillary wicking) of shorter skirt lengths during outdoor exposure, Siloxel™-coated G10 fiberglass insulating skirts of 0.25 inch and 0.5 inch were compared at rain forest (Manoa) and severe marine (MCBH) environments for 72 days. The natural salt particles deposited on the Siloxel™ coated skirts, and galvanic corrosion rates were higher for the shorter skirt length contrary to the laboratory humidity chamber results, indicating that the capillary wicking mechanism was not dominant in the field. In outdoor field environments, since natural salt particles (on the order of a few microns) are deposited on the substrate and not sprayed in solution as in the laboratory experiments, the capillary-wicking mechanism does not have a chance to operate in the absence of substantial rain. To study the effectiveness of different coatings as a function of coating contact angle, CFR PMC/Al galvanic couples with 0.50 inch insulating skirts coated with either the Siloxel™ , an epoxy coating, or no coating were also exposed at the MCBH test site. The CFR PMC/Al galvanic specimens at the severe marine site were exposed in the sheltered and unsheltered conditions. The higher contact angle SiloXelTM-coated G10 induced greater attenuating of galvanic corrosion in the sheltered condition; whereas, the epoxy-coated G10 induced greater attenuation in the unsheltered condition. In the unsheltered condition, the epoxy matrix of the G10 fiber glass substrate degraded due to exposure to sunlight causing the Siloxel™ coating (only several microns thick) to debond and crack resulting in a loss of hydrophobicity; whereas, the much thicker epoxy coating retained its integrity for the duration of the test and hence induced better attenuation. *Raghu Srinivasan and Lloyd Hihara, “Utilization of Hydrophobic Coatings on Insulative Skirts to Attenuate Galvanic Corrosion between Mechanically-Fastened Aluminum Alloy and Carbon-Fiber Reinforced Polymer-Matrix Composites”, Electrochemistry Communications, Volume 72 (2016).

Underwater Acoustic Communication Quality Evaluation Model Based on USV

The unmanned surface vehicle (USV) integrated with acoustic modems has some advantages such as easy integration, rapid placement, and low cost, which becomes a kind of selective novel node in the underwater acoustic (UWA) communication network and a kind of underwater or overwater communication relay as well. However, it is difficult to ensure the communication quality among the nodes on the network due to the random underwater acoustic channel, the severe marine environment, and the complex mobile node system. Aiming to model the communication characteristics of the USV, the multipath effect and Doppler effect are main concerns for the UWA communication in this paper, so that the ray beam method is utilized, the channel transmission function and the channel gain are obtained, and the mobile communication quality evaluation model is built. The simulation and lake experiments verify that the built mobile UWA communication quality evaluation model on USV can provide preference and technique support for USV applications.

Extreme wave analysis methods in the gulf of Cagliari (South Sardinia, Italy)

The aim of the present paper is to compare the results of the most commonly used extreme wave analysis methods applied to a 20 year (1994–2013) wave hindcast record at a grid point in the Gulf of Cagliari (South Sardinia, Italy). This analysis is a part of a large activity to support design, maintenance and repair of the jetty of the SARAS oil terminal in the inner part of the gulf. The paper shows some merits and hindrances of these methods. While conventional distributions recommended by Goda (e.g. the Gumbel and Weibull distribution) represent nowadays the most common methods in those engineering applications, accurate results in the paper indicate that the coastal engineering community should consider the Generalized Pareto Distribution (GPD) as one of the most performing credible candidates. Particular attention should be paid to the large uncertainty in the return level of extreme significant wave height when predicting a reference value for structures operating in a severe marine environment.

Mastering the Arctic marine environment: organizational practices of Pomor hunting expeditions to Svalbard (Spitsbergen) in the eighteenth century

ABSTRACTWe consider the foundations of the widely recognized reputation of the Pomors as experts in dealing with the severe and unpredictable marine environment of the White and Barents Seas. Our research focuses on the history of Russian exploitation of Spitsbergen. Though these kinds of activities occupied only 1% of maritime shipping in the Russian North, the history of exploitation of this Arctic archipelago is contextualized within the history of the Russian North and the lives of its people. Thus, it provides an informative model for general understanding of the methods and structures Pomors used to control the marine environment. The paper is based on newly discovered documents that allowed us to analyse the social and property status of organizers and participants in Spitsbergen hunting. We also consider practices linked to trip organization and supply. We argue that an understanding of Spitsbergen hunting management reveals the general principals of Pomor mastery of the Arctic environment. Flexibility and decentralization of economic activities permitted peasants of the Russian North to demonstrate stable and positive economic results under severe conditions. This could easily have been perceived as a special ability to live in the Arctic.

Corrosion Morphologies in Different Welding Zones of Friction-Stir Welded (FSW) Aluminum Alloy AA5086AA5086, AA6061AA6061, and Dissimilar AA5086AA6061 Joints Exposed in Various Atmospheric Environments

Similar and dissimilar joints of AA6061-T6 and AA5086 have been exposed in mild and severe marine, volcanic (with acid rain), rainforest, and arid atmospheric environments in the Hawaiian islands. The severe marine environment on the Marine Corps Base Hawai'i (MCBH) shows high humidity and rainfall and high chloride ion concentrations; whereas, the mild marine site on Coconut Island is characterized by a significant lower chloride ion concentration. Samples near the Kilauea Volcano on the Big Island are under exposure of acid rain, variable humidity, and sulfur dioxide plume. The rainforest at the Lyon Arboretum in Manoa represents the wet climate with high rainfall, high humidity and time of wetness, and low chloride ion concentrations. In contrast, the dry climate in Waipahu shows low humidity and rainfall, low time of wetness, and low chloride ion concentrations. The impact of the atmospheric environment on the severity of the corrosion has been studied in different welding zones of each type of sample. The focus was to show the dissilimarities in morphology of the parent material, the weld nugget, the heat affected zone (HAZ), and the thermo-mechanically affected zone (TMAZ). The microstructure and chemical composition of the different welding zones before and after the exposure to the environment have been characterized using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Analysis (EDXA). In addition to the field tests, laboratory tests have been performed to study galvanic corrosion between the different welding zones using the zero-resistance ammeter (ZRA) technique.

Corrosion of Aluminum Alloy-Polymer Matrix Composite Interfaces in Diverse Natural Atmospheric Environments

The environmental corrosion of carbon-fiber/epoxy and E-glass/epoxy composite laminated aluminum alloys [e.g., Al 1100-H14, Al 5456-H116 (non-sensitized), Al 5456-H116 (sensitized), and Al 7075-T6] was studied to characterize the interfacial corrosion between the composite and the aluminum substrate. Samples were exposed at 5 locations around the islands of Hawai’i that represented alpine, marine, severe marine, rainforest, and volcano environments over 1-month, 6-month, and 12-month time periods. After exposure, the samples were then adhesion strength tested by conducting pull test to remove the composite laminate from the aluminum substrate to determine the loss (if any) of the composite laminate adhesion to their respective aluminum substrates. The delaminated samples were then analyzed with a scanning electron microscope and energy dispersive X-ray analysis to determine the distribution of corrosion products and ionic species at the aluminum substrate - composite laminate interfaces. The decay in adhesion strength was correlated to the amount of corrosion at the interface that was dependent on the type of composite and type of aluminum alloy.

Challenges and strategies involved in designing and constructing a 6 km immersed tunnel: A case study of the Hong Kong–Zhuhai–Macao Bridge

A 6km immersed tunnel of the Hong Kong–Zhuhai–Macao Bridge (HZMB) has been designed and funded. Once completed in 2016, the HZMB Tunnel will break the record of the 5.8km BART Tunnel in the United States, although it will soon be overtaken by the ∼20km Fehmarn Tunnel between Denmark and Germany that is to be completed in 2020. Construction of the HZMB Tunnel was started in 2011 and more than ten elements thus far have been installed on the site. This paper presents details about the challenges and solutions for the design and construction of the HZMB Tunnel on a strategic level. Special features of the HZMB Tunnel include a long length of 6km, a deep water depth of almost 45m, and a thick backfill of 23m. Challenges include severe marine environment, strict requirements for waterproofing, construction of sections connecting the tunnel with artificial islands, and tunnel stability after future excavation of fairway trenches. Moreover, the HZMB Tunnel is challenged by possible sand liquefaction in seismic events, conservation of white Chinese dolphin, and waterway dispersion during construction. Details about the strategies are given in order to improve the immersed tunnel design and construction methods.

The Effects of Hydrophobic Coatings on an Insulative Skirt Layer to Decouple Galvanic Corrosion Between Mechanically-Coupled Aluminum Alloy and Carbon-Fiber Reinforced Polymer-Matrix Composites

Lightweight metals such as aluminum (Al) are being frequently coupled to polymer-matrix composites (PMCs) to reduce weight and improve performance in a multitude of applications in the defense, aerospace, automotive and civil-infrastructure industries. The intimate contact of carbon-fiber reinforced (CFR) PMCs with Al alloys can result in galvanic corrosion of the Al alloys. The electrically conductive carbon fibers in the CFR PMCs serve as cathodes and induce galvanic corrosion of the Al. The galvanic corrosion between 6061-T6 Al and CFR PMC can be effectively attenuated by decoupling Al from CFR PMC using an insulating skirt layer. The deposition of salts on the insulative skirt, however, can create a continuous ionically-conductive electrolyte film that can bridge the CFR PMC and Al, thus reducing the effectiveness of the skirt. The utilization of hydrophobic coatings on the skirt can help to attenuate galvanic corrosion by breaking up the continuous electrolyte film. In this study, the effect of hydrophobic coatings on insulative skirt materials was investigated to attenuate galvanic corrosion between mechanically coupled 6061-T6 Al and CFR PMC. Experiments were conducted in accelerated laboratory and outdoor conditions. The galvanic corrosion rates were monitored for coatings of different degrees of hydrophobicity, various skirt lengths, and exposure conditions and. Initially, the galvanic corrosion rates for couples with different insulating-skirt lengths coated with a silane-based ceramer (i.e., Siloxel) were monitored in a humidity chamber at 30o C and 90% RH over a period of up to 3 days using the zero resistance ammeter (ZRA) technique. The couples were sprayed with salt solutions of different concentrations. Results from this accelerated humidity ZRA experiment showed that a skirt length of only 0.5 inch was very effective in attenuating galvanic corrosion. To study the effectiveness of different coatings, specimens were fabricated with a 0.5-inch long skirt and coated with either Siloxel, epoxy, polyurethane or latex. The resulting galvanic corrosion rates were then compared. The two best coatings in attenuating galvanic corrosion (i.e., Siloxel and polyurethane) were selected for outdoor exposure. CFR PMC/Al galvanic couples with 0.5 inch insulating skirts (with either the Siloxel or polyurethane coatings, or no coatings) were exposed at rain forest (Manoa) and severe marine (MCBH) environments for 2 months. The CFR PMC/Al galvanic specimens at the severe marine site were exposed in two conditions: sheltered and unsheltered. The sheltered specimens were subjected to significant salt build up; whereas, the unsheltered specimens were subjected to cleansing effects of rain. The effect the salt deposition characteristics on galvanic corrosion between the sheltered and the unsheltered conditions was studied.

Prediction of RC structure service life from field long term chloride diffusion

It is well-documented that the major deterioration of coastal RC structures is chloride-induced corrosion. Therefore, regional investigations are necessary for durability based design and evaluation of the proposed service life prdiction models. In this paper, four reinforced concrete jetties exposed to severe marine environment were monitored to assess the long term chloride penetration at 6 months to 96 months. Also, some accelerated durability tests were performed on standard samples in laboratory. As a result, two time-dependent equations are proposed for basic parameters of chloride diffusion into concrete and then the corrosion initiation time is estimated by a developed probabilistic service life model Also, two famous service life prediction models are compared using chloride profiles obtained from structures after about 40 years in the tidal exposure conditions. The results confirm that the influence of concrete quality on diffusion coefficients is related to the concrete pore structure and the time dependence is due to chemical reactions of sea water ions with hydration products which lead a reduction in pore structure. Also, proper attention to the durability properties of concrete may extend the service life of marine structures greater than fifty years, even in harsh environments.

Prediction of RC structure service life from field long term chloride diffusion

It is well-documented that the major deterioration of coastal RC structures is chloride-induced corrosion. Therefore, regional investigations are necessary for durability based design and evaluation of the proposed service life prdiction models. In this paper, four reinforced concrete jetties exposed to severe marine environment were monitored to assess the long term chloride penetration at 6 months to 96 months. Also, some accelerated durability tests were performed on standard samples in laboratory. As a result, two time-dependent equations are proposed for basic parameters of chloride diffusion into concrete and then the corrosion initiation time is estimated by a developed probabilistic service life model Also, two famous service life prediction models are compared using chloride profiles obtained from structures after about 40 years in the tidal exposure conditions. The results confirm that the influence of concrete quality on diffusion coefficients is related to the concrete pore structure and the time dependence is due to chemical reactions of sea water ions with hydration products which lead a reduction in pore structure. Also, proper attention to the durability properties of concrete may extend the service life of marine structures greater than fifty years, even in harsh environments.

Comparative evaluation of the leakage current and aging performance of htv sr insulators of different creepage lengths when energized by ac, dc+ or dc– in a severe marine environment

This paper compares the performance of HTV (high temperature vulcanized) silicone rubber power line insulators under AC and both polarities DC when subjected to natural pollution. The investigation was conducted at Koeberg Pollution Test Station (KIPTS) which is situated near Cape Town and is known for its severe coastal pollution and high humidity during the night. High rainfall is experienced during winter. Five insulators of different creepage lengths and of the same manufacture were energized by each voltage type, while being exposed to the environment for 310 days. The leakage current data of all insulators were logged, together with the weather data. Pollution levels were measured on a regular basis, using the ESDD (equivalent salt deposit density) method and directional dust deposit gauges (DDDG). High leakage current levels were recorded in summer due to the high pollution levels and high humidity. During winter, in contrast, lower levels of leakage current were recorded, confirming the washing effect of the winter rain. The leakage current levels for the silicone rubber insulators were of a similar order of magnitude for AC and positive DC, but lower for negative DC. Electrical discharge activities on the insulators were recorded at night and surface erosion was monitored at set intervals. A polarity effect relating to pollution performance and aging was confirmed on DC energized insulators.

Stability Evaluation of a Quay Wall of Large Cylinders

The stability of the quay wall incorporating large diameter cylinders is of great concern at the Yangshan Port, China, owing to severe marine environment. In this study, finite element analysis is carried out to evaluate the stability of a trial quay wall during construction. The single cylinder is examined in terms of turnover failure subjected to a five year design wave action. The case when the cylinder is empty is the critical situation during construction. Filling the cylinder right after the installation is an effective way to increase the stability. After the quay wall has been formed by joining the single cylinders, the safety against overturning is reevaluated. The factor of safety of the quay wall is assessed to be 1.5 under a fifty year design wave action.

Reinforcement corrosion initiation and activation times in concrete structures exposed to severe marine environments

The corrosion of steel reinforcement bars in reinforced concrete structures exposed to severe marine environments usually is attributed to the aggressive nature of chloride ions. In some cases in practice corrosion has been observed to commence already within a few years of exposure even with considerable concrete cover to the reinforcement and apparently high quality concretes. However, there are a number of other cases in practice for which corrosion initiation took much longer, even in cases with quite modest concrete cover and modest concrete quality. Many of these structures show satisfactory long-term structural performance, despite having high levels of localized chloride concentrations at the reinforcement. This disparity was noted already more than 50 years ago, but appears still not fully explained. This paper presents a systematic overview of cases reported in the engineering and corrosion literature and considers possible reasons for these differences. Consistent with observations by others, the data show that concretes made from blast furnace cements have better corrosion durability properties. The data also strongly suggest that concretes made with limestone or non-reactive dolomite aggregates or sufficiently high levels of other forms of calcium carbonates have favourable reinforcement corrosion properties. Both corrosion initiation and the onset of significant damage are delayed. Some possible reasons for this are explored briefly.

Prediction of the long-term durability of lightweight aggregate concrete mixtures under severe marine environment

As part of the U.S. Navy program for the Modular Hybrid Pier development, a predictive durability analysis has been carried out to establish the feasibility of using lightweight aggregate concrete mixtures to achieve the 100-year design life under severe marine conditions. The long-term durability of concrete was predicted using both laboratory testing and numerical modeling.

The electrochemical study on mechanical and hydrogen embrittlement properties of HAZ part as a function of post-weld heat treatment in SMAW

Marine structures exposed to severe marine environment should be protected against corrosion in an appropriate way. The cathodic protection method is being widely used in marine structural steel, however, high strength steel for marine structures is easily affected by hydrogen embrittlement (HE) at heat affected zone parts due to over-treatment during impressed current cathodic protection. Elongation and time to fracture were decreased due to HE with shifting to low potential, however, the susceptibility of HE was decreased by post-weld heat treatment (PWHT). It is suggested that an optimum cathodic protection potential not causing HE is from −770 mV (SCE) to above −875 mV (SCE) regardless of PWHT condition.

Atmospheric Corrosion Resistance of Skyward- and Groundward-Exposed Surfaces of Zinc- and 55% Al-Zn Alloy-Coated Steel Sheet

Abstract Zinc-coated (galvanized) and 55% Al-Zn alloy-coated steel sheet was tested for atmospheric corrosion resistance for 20 years in rural (Saylorsburg, Pennsylvania), industrial (Bethlehem, Pennsylvania), moderate marine (250-m [880-ft] lot, Kure Beach, North Carolina), and severe marine (25-m [80-ft] lot, Kure Beach, North Carolina) environments. Corrosion losses were determined separately for skyward- and groundward-exposed surfaces and compared to results for conventional two-sided coupons, which gave only an average of skyward and groundward surfaces. Results were fitted to exponential equations of the form C = ATB, where C is the corrosion loss, T is time, and A and B are constants. Coating lives were estimated based upon extrapolation of these equations to the time to reach a corrosion loss equal to the coating thickness. On average, the estimated life of a skyward-exposed 55% Al-Zn alloy coating was 12 times that of a galvanized coating of equal thickness (25 μm).

Composite Repair of a Stainless Steel-GRP Sonar Dome

This paper describes the application of composite materials for the repair of corrosion damage on stainless-steel components of hull-mounted sonar domes on typical warships. The domes have an aerofoil shape in plan, approximately 4.08 m nose to tail, 1.27 m maximum width, and 1.83 m high. The sides (acoustic window) of the domes are made of stainless steel and the canoe-shaped bottom is made of glass-reinforced plastic (GRP) composite. A bottom-mounted stainless-steel insert and drain plug unit is used for flooding and draining the dome. Due to the severe marine environment, the stainless steel drain plug suffers extensive corrosion damage and has to be replaced frequently. A study performed to replace the stainless-steel insert and drain plug components with composite material is presented. The approach adopted is to treat the problem as a flush composite repair, whereby an area around the drain hole in the GRP canoe is cut out and replaced with a two-piece composite insert that is bonded onto the GRP canoe. Both the insert and plug are made of glass-reinforced composite material. Details of the material selection, design, fabrication, and process specification for the repair, as well as the challenges involved in undertaking this repair are discussed.

厳しい塩害環境下での鉄筋コンクリート構造物の耐久性に関する研究 : アクリルゴム系防水塗膜の効果

A field reinforced concrete structure with and without an acrylic rubber-based surface coating was built in Okinawa for this research project, and it has been exposed to severe marine environment for ten years. The test on this structure gives the following results : (1)In unprotected concrete, the penetration of chloride ions into concrete is very rapid, and the corrosion of reinforcing bars occurs in early stage. (2)The acrylic rubber-based surface coating acts as a complete barrier to the transport of chloride ions, water and oxygen, and prevents the corrosion of the bars in chloride-contaminated concrete.

The performance of a 12% chromium steel in concrete in severe marine environments

3CR12, essentially a 12% Cr steel, was used in two series of exposure programmes to assess its performance as reinforcing in concrete. In the first exposure programme, steel and 3CR12 in the pickled and passivated condition were exposed in a specially designed marine climate simulator. Comparative performance after 4 1 2 years exposure confirmed 3CR12 as a viable durable reinforcing material for concrete. In the second exposure programme, steel, 3CR12, 316 and 304 stainless steel were exposed in the hot rolled condition (scale intact). Galvanised steel and powder epoxy coated rebar were also exposed. Exposures were carried out at a severely corrosive marine site and in the simulator. Within 2 years, the results from this programme emphasized the need to remove all hot-roll scale from the 3CRI2, the 316 and 304 stainless steel rebars before being used as reinforcing in concrete. Galvanized steel rebars performed poorly. Powder epoxy coated rebars showed severe under-rusting and corrosion. By comparison steel rebars performed extremely badly. Despite the highly alkaline conditions (i.e. the absence of carbonation), chloride penetration caused severe corrosion; the chloride front penetrating through 25 mm of good concrete cover within 2 years.