Seawater Service Research Articles

Corrosion Studies of AA2024 in Sea Water using Sodium Benzoate as an Inhibitor

Many different types of destructive attack can occur to marine structures, ships and other equipments used in sea water service. Year upon year the cost of marine corrosion has increased until it is estimated today at 4% of the Gross National Product. Aluminium alloys are important materials and commonly used in marine applications. In this aluminum 2024 were subjected to seawater. Sodium Benzoate was used as corrosion inhibitors for aluminium alloy in aggressive marine environment. In order to study the corrosion behavior of aluminum alloy AA2024 in seawater, the electrochemical behavior of aluminum alloy was investigated with different inhibitor concentrations, potentiodynamic polarization and electrochemical spectroscopy (EIS). The morphology study was carried out to observe the development of thin film on the specimen and this study was performed using Scanning Electron Microscopy (SEM). EIS data showed that the mechanism of corrosion depends on inhibitor concentration.

Poly(trialkylsilyl methacrylate)s: A family of hydrolysable polymers with tuneable erosion profiles

Polymers containing hydrolytically labile trialkylsilyl ester side groups were synthesised via a conventional and a controlled radical polymerization. The trialkylsilyl methacrylate monomer unit was chosen for its capacity to hydrolyse into basic, acid or sea water varying the hydrophilic character of the resulting polymer backbone with time. The hydrolysis or saponification reaction of the ester bond of the trialkylsilyl methacrylate was monitored through a 1H NMR study showing the formation of siloxane side-products. Several copolymers and polymer blends were prepared as matrixes for controlled erodible systems. Their capacity to hydrolyse was demonstrated through SEM investigations with selective dissolution of free films containing hydrolysable copolymers and PMMA blends. Well-defined random and diblock copolymers with methyl methacrylate were investigated to show the effect of the microstructure on the erosion properties of the corresponding coatings. Poly(methyl methacrylate-b-tert-butyldimethylsilyl methacrylate) diblock copolymers synthesised through the RAFT process showed a better control of the erosion with a constant erosion rate over a long-time service in sea water at pH = 8.2. In addition, experiments showed that the erosion rate could be modulated by varying the molar proportion of hydrolysable side groups onto the copolymer backbone and the weight amount of copolymers mixed with PMMA in toluene solution.

Mathematical model for calculating the strength of a single lap adhesive joint intended for the service in sea water

AbstractThe application of adhesives in the joining of materials is limited not only by the impossibility of accurately calculating the strength of an adhesive bonded joint, but also by incomplete knowledge of effect of service conditions upon degradation of adhesive forces. This is particularly true for adhesive bonded joints intended for service in sea water. In the introductory part of the paper, the effects of liquids upon the strength of adhesive bonded joints are described as reported in the reference publications. Difficulties encountered in using adhesive bonded joints in liquids and other media with high humidity are considered. In the experimental part of the paper, the authors endeavour to explain the effects of sea water upon the strength of single lap adhesive bonded joints of high alloyed steel.Neben der Unmöglichkeit der exakten Klebungsfestigkeitsberechnung, ist die Unkenntnis der Adhäsionsschwächung mit der Zeit eine Einschränkung für die Klebtechnikanwendung insbesondere bei der Anwendung unter Meerwasser. In der Einführung dieser Arbeit wird die Auswirkung von Flüssigkeiten auf die Klebfestigkeit nach Literaturangaben beschrieben und es werden die Schwierigkeiten bei der Klebanwendung in Flüssigkeiten und Medien mit großer Feuchtigkeit angezeigt. Im experimentellen Teil der Arbeit wird untersucht wie sich die Meereswassereinwirkung auf die Festigkeit von einschnittig überlappten Klebverbindungen an hochlegierten Stählen auswirkt.

Evaluation of superaustenitic stainless steels as construction materials in sea water service systems

Evaluation of superaustenitic stainless steels as construction materials in sea water service systems

Field and laboratory study of cavitation corrosion of nickel aluminium bronze in sea water

AbstractA case study of a nickel aluminium bronze vertical type pump that failed during service in sea water and a laboratory investigation of the cavitation corrosion behaviour of the cast alloy are reported. The failure of the pump was found to result essentially from cavitation damage and erosion corrosion grooves. Other factors such as sulphide attack and preferential phase corrosion played a secondary role. The preferential attack occurred at the boundaries between the copper rich α-phase and the intermetallic K precipitates. It had an average depth of penetration ranging from 17 to 48 μm. In laboratory tests, the presence of cavitation was found to shift the free corrosion potential of the material in the active direction by 65 mV: It also increased the cathodic and anodic currents during polarisation by an order of magnitude. The rate of mass loss in the presence of cavitation was found to be 186 times that under quiescent condition. Cathodic protection reduced the rate by 47% with respect to that ...

Effectiveness of cathodic protection of UNS N04400 heat exchanger tubes for sea water service

Abstract A detailed laboratory study was performed to assess the use of carbon steel sacrificial anodes to galvanically protect UNS N04400 nickel alloy heat exchanger tubes in sea water applications. Several parameters were investigated: the potential-time relationship of uncoupled and coupled steel-N04400, the current-time relationship of the coupled alloys, the effect of a two sacrificial anode system, the effect of water path length, and the effect of new and used N04400 alloy tubes. Data analysis indicated that the application of sacrificial cathodic protection to N04400 heat exchanger tubes in sea water applications will prevent pitting corrosion and thus prolong tube service life.

Effectiveness of cathodic protection of UNS N04400 heat exchanger tubes for sea water service

Effectiveness of cathodic protection of UNS N04400 heat exchanger tubes for sea water service

Technical note: Localised corrosion of electric resistance welds of austenitic stainless steel in sea water

An investigation was conducted on prematurely failed titanium stabilised austenitic stainless steel tubes of a heat exchanger used in sea water service. The tubes were longitudinally welded using the high frequency electric resistance welding technique. The investigation showed the failure to be due to pitting and crevice corrosion at the weld. The attack occurred at discrete sites and the deposits inside the pits were rich in chromium and iron. The corrosion of the tubes was attributed to depletion of chromium and molybdenum from the austenite phase. This depletion was ascribed to coarsening of the delta ferrite phase as a result of high heat input during welding.

A photoelectrochemical characterization of passive films on stainless steels

Passive films on stainless steels for sea water service have been studied by means of photocurrent measurements. Four experimental ELI (Extra Low Interstitital) ferritic stainless steels (types 25Cr-4Ni-4Mo) and a commercial superaustenitic stainless steel (type 20Cr-18Ni-6Mo-N) have been investigated. Differences in the photoelectrochemical behaviour have been attributed to the different nature of the passive films grown on ferritic or superaustenitic stainless steels. An interpretation is provided to explain the complex dependence of the photocurrent transients on the applied potential. Manuscript received 27 February 1986; in amended form 19 June 1986.

海水中におけるステンレス鋼のすき間腐食と使用条件との関係

In order to study the crevice corrosion of austenitic stainless steels which often occurs in stainless steel piping or heat exchanger tubing used for sea water service, the effects of chemical composition of steels, contents and flow velocity of sea water, heat transfer conditions and cathodic protection have been studied. Both plates and tubes made of 20Cr-22Ni-5Mo steels with nitrogen content of 0.02 to 0.2% and of commercial stainless steels (SUS 304, SUS 316L, SUS 329J1 and 20Cr-26Ni-6.5Mo) were evaluated, and copper base alloys (aluminum brass and cupro-nickel) were also tested in an experiment.All results of electrochemical tests (anodic polarization curves, passivation behaviors and constant potential tests in 0.1N-HCl+2M-NaCl and 1N-HCl solution at 60°C), model sea water heat exchanger tests (tube side: sea water of 0.5 to 1.5m/sec., shell side: water or steam of 50°C to 140°C, 1 year ran), and concentrated sea-water flow-through tests (twofold of sea-water at ambient temperature) indicated that newly developed 20Cr-22Ni-5Mo-0.2N steel had a considerably higher resistance to crevice corrosion in sea-water environments, in comparison with commercial stainless steels and copper base alloys, but care should be taken on the using condition in actual service.

Effect of thermal cyclings and a corrosive environment on the condition of the surface layer and performance of gas-turbine blades

bility of the heat-resistant heterophase alloy in the intermediate layers [1-5, etc.]. Specifically, such structural instability includes the following effects: a change in the fine structure characteristic of the solid solution of the metal (microstresses and cell dimensions); redistribution of the main alloying elements under the influence of temperature and the formation of new phases; formation of secondary structures due to the reaction of alloying elements with the components of fuel combustion products; recrystallizatio n of the plastically deformed surface layer, etc. The present work investigates the performance of gas turbine blades and the condition of their surface layer under the thermocyclic and corrosive effects of a high-temperature gas stream, including one to which marine salts have been added. The condition of the surface layer of the blades was evaluated by studying changes in the parameters of the fine structure, microstructure, and chemical composition of the surface layers of the blade material after tests on a gasdynamic stand. Structure was studied by metallographic and x-ray diffraction methods and the method of x-ray microspectroscopy. In the x-ray diffraction analysis, we studied specimens cut from the inlet edge of the blades at different stages of thermocycling (service), using a DRON-2 diffractometer and copper K~-radiation. Microdistortions and regions of coherent scattering (RCS) were calculated using the method of approximation in [i] on an electronic digital computer. The content of chemical elements was determined on a "CAMECA" microanalyzer by scanning the specimen under an electron probe from the middle to the surface. The element concentrations shown below were computed with allowance for correction factors on an electronic digital computer. The performance of gas-turbine blades was studied on the gasdynamic stand of the Institute of Strength Problems of the Ukrainian Academy of Sciences in a thermocyclic, corrosive high-temperature stream of fuel combustion products, including a stream containing marine salts. The experimental method and equipment were described in [2]. We tested models of GTE rotor blades made of alloys ~P220 and ~I827. The tests were conducted with a cyclic change in the temperature of the gas stream within the range 250I150~ Here, the temperature of the metal of the inlet edge of the blades changed within the range 920-440~ Heating time in each cycle was 5 sec, cooling time i0 sec. To simulate the conditions of GTE service in sea water, we added to a gas stream of kerosine combustion products synthetic seawater with a content of 1 mg of salts per 1 m s air. For comparison, we also conducted tests without marine salts in the gas stream.

The Successful Use of Austenitic Stainless Steels in Sea Water

Moller, G.E., International Nickel Co., Inc., Torrance, Calif. Abstract Austenitic stainless steels are providing excellent trouble-free service in sea water for pumps, propellers, valves. and other marine equipment. propellers, valves. and other marine equipment. Occasionally, a failure occurs as the result of deep localized pitting in a crevice. Data are given showing that austenitic, ferritic. and martensitic stainless steels suffer pitting in crevices and under deposits in quiescent sea water. Austenitic stainless steels remain free from attack in high-velocity sea water. Low-purity ferritic and the martensitic stainless steels frequently pit in high-velocity sea water. Crevice corrosion can be controlled effectively with cathodic protection from iron, zinc. aluminum or magnesium galvanic anodes or impressed current cathodic protection by polarization to -0.6 v vs Calomel. Austenitic stainless steel performs well in many situations because it is a component of a multi-alloy assembly utilizing iron or steel. Examples from field experience arc given. Introduction During the past decade, there has been a growing use of austenitic stainless steel in marine equipment. Most applications have been successful but an unexpected failure has been observed occasionally. It is the purpose of this paper to describe when and how to use austenitic stainless steel with success. The selection of stainless steels appears to result from the engineering requirements of new, advanced, high-speed, high-reliability commercial, pleasure, and military craft. Ocean science and pleasure, and military craft. Ocean science and engineering, offshore oil production, fishing, and ocean mining are also contributing to the selection of stainless steels for sea-water applications. The increasing use of stainless steel in the marine environment is found in work-boat propellers, pump components, bow thrusters, valves, shafting pump components, bow thrusters, valves, shafting and shaft components, through-hull fittings, parts on data-gathering buoys, fasteners, and housings of oceanographic instruments. When austenitic stainless steel has given good, corrosion-free service, it is most often found to be used as a key component in a multi component, multi-alloy assembly or system receiving the benefit of built-in cathodic protection. For example, in Fig. 1 a cast Type 304 (Alloy Casting Institute CF-4) propeller is being used on a steel seagoing tugboat with zinc anodes attached to the rudder. Fig. 2 shows a cast ACI CE-30 power-plant sea-water circulation-pump impeller free power-plant sea-water circulation-pump impeller free of any corrosion after 6 years of service that was used in combination with an austenitic cast-iron suction bell and diffuser. SPEJ p. 101

Corrosion of Metals in Tropical Environments

Abstract Eight-year exposure tests of six stainless steels to underwater and atmospheric environments in Panama Canal Zone are described. Test environments included sea water immersion, lake water immersion, seashore inland, inland, sea water mean tide, and seashore. Structural steels, phosphor bronze and naval brass were also evaluated for comparison. Stainless steel plates later were galvanically coupled to carbon steel strips for testing in tropical waters. Stainless steels were not recommended for sea water service where perforation of structure is a consideration. They gave excellent results, however, in tropical fresh water. Tropical atmospheres appeared more corrosive to stainless steels than did temperate climates. 4.2.7, 6.2.5

CORROSION—Metals for Sea Water Service

CORROSION—Metals for Sea Water Service

Rubber and Synthetic Linings Give Good Sea Water Service

Rubber and Synthetic Linings Give Good Sea Water Service