DEMM Engineering & Manufacturing

Onsite portable XRD corrosion analysis

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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.

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