Onsite portable XRD corrosion analysis
The economic i mpact of all types of corrosion and its degradation of infrastructure, such as pipelines, oil rigs and towers, represents an annual cost of many billions of dollars to industry. In a 2016 report issued by NACE (USA) this was estimated to be more than three percent of annual global GDP. In addition to being an economic threat to industry and the wider community, corrosion can also be a physical threat to infrastructure and the safety of staff and members of the public.
Effective corrosion management strategies can help reduce the cost. A key part of such a program is the rapid identification of the corrosion and scaling products so that the appropriate controls are implemented. For remote mining operations or off-shore oil production facilities, the cost of testing any sort of sample is increased by the need to transport it to a specialist laboratory. Even within major cities and regional centres it can often take weeks for laboratories to analyse samples.
There are also intangible costs that can have a significant impact upon businesses and the wider community. Any disruption to production at an oil refinery or steel manufacturing plant can cost hundreds of thousands of dollars or more – in any currency - each day.
One analysis technique that can be used in corrosion management is X-ray diffraction ( XRD). According to Dane Burkett, Product Specialist with Olympus, “Traditional analysis of corrosion products only indicates their presence, or their chemical composition, such as iron (Fe) -bearing corrosion. XRD can identify and quantify corrosion and scaling products – for example magnetite or akaganeite – by characterising their crystallographic structure.” A geologist by training, Burkett’s role involves meeting with clients to determine their analysis requirements, in addition to application support.
To ensure efficient and productive use of a mining or production asset, a corrosion engineer or chemist needs the analysis information fast so they can
best identify the corrosion products and plan and implement repair and maintenance strategies accordingly.
The time taken to get a sample from an offshore asset to a lab with XRD capabilities can take weeks and cost a company thousands of dollars, in addition to the cost of the downtime of their asset.
However, comprehensive compositional materials analysis can now be carried out onsite using the field portable Terra XRD and XRF analyser from Olympus. “Using a Terra unit, our customers can analyse their samples directly on an oil platform, remote plant or refinery,” Burkett said. “The results can then be transmitted back to a corrosion expert – either on or off-site – to help devise a solution.”
The crystallographic structure of corrosion and scaling products is unique, much like a fingerprint, and XRD is used to define this characteristic structure. XRD works by subjecting a sample to a monochromatic X-ray beam and measuring the angles at which the X-rays diffract. A combination of diffraction angles is characteristic of a given phase of a particular corrosion or scaling product.
Unlike other methods – such as infra-red spectroscopy – which identify compounds, XRD can identify and quantify all crystalline phases, irrespective of reflectance. (Opaque phases such as magnetite cannot be identified using infra-red spectroscopy.)
In addition, XRD can distinguish between different corrosion and scaling products that have the same, or similar chemistry. For example, the ferrous corrosion products goethite, lepidocrocite, feroxyhyte and akaganeite can be distinguished from each other, even though they all have the chemical formula FeO(OH).
The identification of compounds (as opposed to elemental compositions) is crucial for the understanding of corrosion processes. “Different corrosion and scaling products form under different conditions and in different environments,” said Burkett. “Information about the presence and quantity of these phases is not only helpful in explaining the corrosion process, but can help to determine the root cause, locate the origin of corrosion in a facility and, at the same time, indicate possible solutions to the problem.”
Once a corrosion or scaling product is identified, it is possible to determine the temperature, pressure, fluid chemistry and pH conditions under which it formed. “If you know what it is then you can determine the best way to treat it,” Burkett added. “This might be with an acid wash or adding some type of inhibitors into the process.” Other treatments include use of, bactericides, alternative or enhanced coatings, milling the inside of the machinery or, ultimately, replacement of the equipment.
Knowing how corrosion products form allows an engineer to optimise a process to stop or slow their occurrence. For example, the temperature or pressure parameters can be adjusted or leaks can be located and repaired.
Olympus customers are using the company’s instruments for routine analysis of corrosion material found at refineries, pipelines, offshore oil platforms, coal fire power generation plants and geothermal plants and drilling sites.
“The application of our instruments to corrosion and scaling are many and varied,” Burkett stated. “Our instruments are being used for root cause analysis of persistent corrosion by inspection companies, through to restoration of historical and archaeological artefacts by museums and universities.
“Corrosion analysis is an exciting application for us,” Burkett added. “Being able to conduct analyses on site with a transportable unit that can be deployed to site can make immense cost savings.”
The Terra portable XRD analyser is a high performance, self- contained, battery operated, closed-beam XRD system that provides full phase identification of major, minor and trace components. The ruggedised and functional unit combines X-ray Diffraction and qualitative X-ray Fluorescence ( XRF) analysis in a single instrument. The Terra delivers savings in operational
Knowing how corrosion products form allows an engineer to optimise a process to stop or slow their occurrence.
costs, space, and time along with seamless integration of data and results. The sample preparation and operation of the analyser do not require detailed technical knowledge so anyone onsite can run the test.
OUT OF THIS WORLD TECHNOLOGY
The technology inside the Olympus Terra was initially conceived to perform chemical and mineralogical testing for NASA’s Mars Science Laboratory (MSL) mission. Combining both Olympus and NASA innovation, the Terra enables a new way of performing XRD and XRF measurements as part of Earthbound applications.
Using a specifically developed direct excitation charge coupled device (CCD) ‘camera’, Terra is able to collect X-ray photon data for both X-ray diffraction and X-ray fluorescence simultaneously. The camera has the ability to detect both photon position and photon energy at the same time. In simple terms, the Terra can simultaneously measure XRD for quantifying corrosion products and XRF for qualitative chemistry. With energy resolution of ~200 eV (5.9 keV), Terra makes XRF analysis as simple as viewing the software spectrum display.
The Terra simplifies sample preparation and loading for X-ray diffraction experiments. The preparation, loading and unloading of samples is so easy, that a technician can be trained to load a sample within a matter of seconds. To ensure a sufficiently random orientation of crystals, the patented sample vibration chamber built into the Terra eliminates the requirement to finely grind – grains < 10 μm – and press the sample into a pellet. Requiring a mere 15 mg sample at < 150 μm, the vibration chamber’s convection process presents the instrument optics with multiple orientations of the crystalline structure. The resulting X-ray diffraction pattern is virtually free of ‘preferred- orientation effects’ often encountered when using conventional, lab-based XRD instruments.
The Terra’s unique powderhandling system, non-mechanical goniometers – used to measure angles – and lack of complicated moving parts, makes it ideal for those applications where field portability and ease of use are important.
Olympus believes it can hold its place at the forefront of the development of X-ray analysis technology which provides fast, non- destructive qualitative and quantitative characterisation of materials. Instruments developed by Olympus can be used for detection, identification and analysis of elements at a range of concentrations.
The Terra can be used in a wide range of applications including oil/gas, geothermal and mineral exploration; mineral processing; mineral identification; mid- stream processing for pharmaceuticals and industrial materials; counterfeit drug screening; fire and explosives forensics; and corrosion monitoring.
Olympus says its development engineers continually investigate different detectors, filtering techniques and analysis algorithms to improve the sensitivity and accuracy of its X- ray analysis systems. Today, the Terra unit provides the advantages of large laboratory based XRD and XRF testing in a fast, portable and cost- effective unit.