Search results
1 – 10 of over 9000Corrosion‐fatigue testing using precracked specimens has, in recent years, become an important means of evaluating structural alloys for service in corrosive environments. The…
Abstract
Corrosion‐fatigue testing using precracked specimens has, in recent years, become an important means of evaluating structural alloys for service in corrosive environments. The recent emphasis towards the use of precracked specimens for corrosion‐fatigue testing is based upon several factors. First, there is the general recognition that metallic structures of all types are prone to contain cracks and that the growth of such cracks can play a crucial role in overall structural performance; and secondly, a fracture mechanics technology basis has been developed for quantitatively assessing crack growth phenomena. The coexistence of a visible problem area and a means of attacking the problem has stimulated considerable activity in this field of endeavour.
Yuhai Qian, Jingjun Xu and Meishuan Li
The purpose of this paper is to present a laboratory accelerated periodic immersion wet/dry cyclic corrosion test, reflecting the alternate wet/dry process during the atmospheric…
Abstract
Purpose
The purpose of this paper is to present a laboratory accelerated periodic immersion wet/dry cyclic corrosion test, reflecting the alternate wet/dry process during the atmospheric exposure of metallic materials, which can be applied to evaluate the atmospheric corrosion resistance (ACR) of weathering steels in a very short period.
Design/methodology/approach
This test method uses 0.01 M sodium bisulfite aqueous solution with pH 4.4 as the immersion medium, simulating the notable characteristics of sulfur dioxide pollutant in industrially polluted atmospheres. During the test process, the tested specimens are immersed into the solution for 12 minutes, immediately followed by the subsequent drying process for 48 minutes, and such alternate process consists of a cyclic period, i.e. 1 hour. As a result of this procedure, a relative corrosion rate is defined to determine the ACR. To determine a preferred test period, different test periods including 72 and 200 hours were compared.
Findings
Compared with several other commonly used test methods, it was confirmed that the relative ACR of various steels can be determined after testing for only 72 hours. The constituent of the corrosion products, i.e. the rust layer, was consistent with that formed after long-term exposure in a typical outdoor atmospheric environment.
Originality/value
The test method enables comparative testing for ranking the ACR of weathering steel during the development of new weathering steels.
Details
Keywords
Examines accelerated methods for the corrosion testing of materials, coatings and surface treatments used in the aerospace and defence industries. The drawbacks with some current…
Abstract
Examines accelerated methods for the corrosion testing of materials, coatings and surface treatments used in the aerospace and defence industries. The drawbacks with some current accelerated corrosion tests are examined, particularly the problems experienced with neutral salt spray tests. Specific examples are given which identify the acute discrepancy between salt spray and marine exposure in the corrosion testing of metallic coatings on steels. Examines some recent advances in corrosion testing of aerospace materials, pre‐treatments and organic coatings, and outlines some preliminary research conducted at DERA Farnborough in developing more accurate test methods.
Details
Keywords
J. Brettle and S. Orman
Introduction The ever increasing demands made on materials by advanced technology has led, in recent years, to a greater awareness of the importance of mechano‐chemical behaviour…
Abstract
Introduction The ever increasing demands made on materials by advanced technology has led, in recent years, to a greater awareness of the importance of mechano‐chemical behaviour. These may be defined as the synergistic effect of mechanical forces and chemical reactions on the material. Although possibly interrelated, three classes of mechano‐chemical reactions have been identified as; stress‐corrosion (SCC), corrosion fatigue (CF) and hydrogen embrittlement. SCC has become one of the ‘in’ subjects of corrosion science during the last decade, while the importance of CF has emerged comparatively recently. In a review of the national corrosion and protection scene in 1970, it was revealed that 62 postgraduate research workers, representing 21% of the total effort in the corrosion and protection field, were involved in mechano‐chemical corrosion studies1. The bulk of these were working on SCC. This large research effort has not resulted in a standardisation of test methods nor, despite several attempts, in a unifying theory for SCC2. The newcomer to the field is faced with a bewildering variety of tests of varying complexity and validity. The supporters of each type of test tend to make exaggerated claims particularly when the test they are advocating is the only one which has caused a particular alloy‐environment system to exhibit SCC.
Bo Hu, Runqiao Yu and Jian Liu
This paper aims to clarify the transient electromagnetic method used for the nondestructive testing of the corrosion of an in-service buried metal pipeline in trenchless state.
Abstract
Purpose
This paper aims to clarify the transient electromagnetic method used for the nondestructive testing of the corrosion of an in-service buried metal pipeline in trenchless state.
Design/methodology/approach
The paper designed corrosion models indoor and infield for testing. A method for calculating the residual wall thickness of metal pipelines was also proposed. The calculation method was verified by the test results. In the test, the receiving probe was improved by the addition of a Mn-Zn ferrite core. The amplitudes of the test results obviously increased, and the calculation accuracy was improved.
Findings
The paper states that the transient electromagnetic method can detect the uniform corrosion distribution of a certain section of a pipeline. A multi-channel profile of the induced electromotive force and the calculated values of the residual wall thickness can be used to confirm the position and degree of corrosion defects, respectively.
Research limitations/implications
The transient electromagnetic method is more effective for large-area corrosion than for localized corrosion (pitting).
Practical implications
The paper includes implications for the development of nondestructive testing method of the corrosion of an in-service buried metal pipeline.
Originality/value
This paper proved the feasibility and reliability of using transient electromagnetic method to test the corrosion of a buried metal pipeline based on experimental study.
Describes methods of accelerated corrosion testing currently being used in the world today and the cabinets available in which to perform the tests. Compares the tests and looks…
Abstract
Describes methods of accelerated corrosion testing currently being used in the world today and the cabinets available in which to perform the tests. Compares the tests and looks at the results obtained from them, looking at constant salt‐spray testing ASTM B117, cyclic wet/dry Prohesion and the multi‐function automotive cyclic corrosion test which incorporates salt‐spray cycles and high humidity cycles. Gives test results comparing constant salt‐spray to cyclic Prohesion to natural outdoor exposure.
B.A. Lasebikan, A.R. Akisanya and W.F. Deans
The purpose of this paper is to develop an autoclave that can be used to assess corrosion behaviour of suitable material in high-pressure–high-temperature (HPHT) environments…
Abstract
Purpose
The purpose of this paper is to develop an autoclave that can be used to assess corrosion behaviour of suitable material in high-pressure–high-temperature (HPHT) environments. Many new discoveries of oil and gas field are in HPHT environments. The development of such fields requires appropriate selection of materials that are able to withstand not just the service loads but also corrosive production fluids in the HPHT environment.
Design/methodology/approach
The exposure of material samples to elevated pressure and temperature is usually done using an autoclave. The suitability of an existing autoclave for HPHT corrosion studies is provided together with suggestions on necessary design modifications. An alternative design of the autoclave is proposed based on functionality requirements and life cycle cost assessment.
Findings
It is concluded that the existing autoclave was unsuitable for HPHT corrosion tests, and modifications were very expensive to implement and/or not foolproof. A new autoclave was designed, manufactured, tested and successfully used to study the effect of aqueous solution on the corrosion of a pipe subject to a combination of axial tension, internal pressure and elevated temperature.
Research limitations/implications
The maximum design pressure of 15 MPa is more than sufficient for high-pressure corrosion studies in aqueous solution where partial pressure of the dissolved gas is one of the main controlling parameters. However, the design pressure is only suitable for corrosion studies in a seawater environment of up to 1,500 m water depth.
Originality/value
A new design of autoclave together with all the necessary piping, assembly and control system is proposed for HPHT corrosion studies. The autoclave can be used as standalone or integrated with a mechanical testing machine and thus enables corrosion studies under a wide range of loading.
Details
Keywords
Madeleine Du Toit and Kalenda Mutombo
This paper aims to characterise the hardness, tensile properties, corrosion behaviour and fatigue properties (in air and in a 3.5 per cent NaCl solution) of aluminium 6061-T651 in…
Abstract
Purpose
This paper aims to characterise the hardness, tensile properties, corrosion behaviour and fatigue properties (in air and in a 3.5 per cent NaCl solution) of aluminium 6061-T651 in the as-received and as-welded conditions.
Design/methodology/approach
Aluminium 6061-T651 plate material, prepared with double-V or square butt joint preparations was welded using semi-mechanised or mechanised pulsed gas metal arc welding. Magnesium-alloyed ER5356 or ER5183 filler material or silicon-alloyed ER4043 filler wire was used. The material was characterised in the as-supplied and as-welded conditions, and fatigue tests were performed in air and in a 3.5 per cent NaCl solution. The fatigue results were compared to the reference fatigue design curves for aluminium published in Eurocode 9 – Part 1-3.
Findings
Significant softening, attributed to the partial dissolution and coarsening of precipitates, grain growth and recrystallisation during welding, was observed in the heat-affected zone (HAZ) of the 6061-T651 welds. During tensile testing, failure occurred in the HAZ of all 6061 welds tested. Welding reduced the room temperature fatigue life of all specimens evaluated. In 6061 welds, failure occurred preferentially in the softened HAZ of the welds. The presence of a corrosive environment (a 3.5 per cent NaCl solution in this investigation) during fatigue testing reduced the fatigue properties of all the samples tested. Corrosion pits formed preferentially at second phase particles and reduced the overall fatigue life by accelerating fatigue crack initiation.
Originality/value
The fatigue properties of welded aluminium structures under dynamic loading conditions have been studied extensively. Welding is known to create tensile residual stresses, to promote grain growth, recrystallisation and softening in the HAZ, and to introduce weld defects that act as stress concentrations and preferential fatigue crack initiation sites. Several fatigue studies of aluminium welds emphasised the role of precipitates, second phase particles and inclusions in initiating fatigue cracks. When simultaneously subjected to a corrosive environment and dynamic loading, the fatigue properties are often adversely affected and even alloys with good corrosion resistance may fail prematurely under conditions promoting fatigue failure. The corrosion-fatigue performance of aluminium welds has not been systematically examined to date.
Details
Keywords
The purpose of this study was to determine correlation between an accelerated cyclic corrosion test (S6‐cycle test) specified in Japanese Industrial Standards K5621 and field…
Abstract
Purpose
The purpose of this study was to determine correlation between an accelerated cyclic corrosion test (S6‐cycle test) specified in Japanese Industrial Standards K5621 and field exposure tests, and to open up applications of the accelerated tests in various regional environments.
Design/methodology/approach
The S6‐cycle corrosion test was carried out on structural steels for 30, 60, 90, 120 and 150 days and metal coating films for 100, 200 and 300 days. Comparing the weight loss of the steels with 1‐, 3‐, 5‐ and 9‐year field exposure test data at 31 sites in Japan. Correlation of the S6‐cycle tests to the field exposure tests was determined by acceleration coefficients.
Findings
The correlation between the S6‐cycle test and the field test on uncoated structural steels can be determined by acceleration coefficients based on flying salt amount. The coefficients were applicable for durability prediction of uncoated, zinc hot‐dip galvanized and painted steels.
Research limitations/implications
In determination of the accelerated coefficients, only the flying salt amount was considered. Others factors such as temperature and humidity will be considered in future work.
Practical implications
Using the S6‐cycle corrosion test and its accelerated coefficients, the thickness loss of uncoated structural steels and zinc hot‐dip galvanizing is predictable in a short time. Corrosion degradation of coated steels is also predictable approximately.
Originality/value
This paper contributes to open up the application of accelerated cyclic corrosion test to evaluating corrosion resistance of steel bridge members.
Details
Keywords
The author of this article reviews those tests for corrosion which have been proved over a long period, the modifications lately incorporated into such tests, and some important…
Abstract
The author of this article reviews those tests for corrosion which have been proved over a long period, the modifications lately incorporated into such tests, and some important testing methods recently evolved which are now widely used in industry.