Name: imaging corrosion at the metal-paint interface using time-of-flight secondary ion mass spectrometry
Uploaded: 2019-05-06T13:00:00
Description: Watch this Scientific Journal Video about Imaging Corrosion at the Metal-Paint Interface Using Time-of-Flight Secondary Ion Mass Spectrometry at JoVE.com

This work was funded by the QuickStarter Program supported by Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the U.S. DOE. This work was performed using the IONTOF ToF-SIMS V, located in the Biological Sciences Facility (BSF) at PNNL. JY and X-Y Yu also acknowledged the support from the Atmospheric Sciences &#38; Global Change (ASGC) Division and Physical and Computational Sciences Directorate (PCSD) at PNNL

1. Corrosion sample preparation
<ol>
	<li>Al sample fixation in resin, and polishing
	<ol>
		<li>Mount two Al alloy coupons (1 cm x 1 cm) using epoxy resin in 1.25 inch metallographic sample cups and place the coupons in the fume hood overnight or till the resin is completely cured.</li>
		<li>Take out the Al resin cylinders cups from the sample cups. Polish the Al resin cylinders using 240 grit paper with water at a 300 rpm platen/150 rpm in the holder for 1 min.</li>
		<li>Polish the Al resin cylinde...

<ol>
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W., Castner, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+Bi(1),+Bi(3)+and+C(60)+primary+ion+sources+for+ToF-SIMS+imaging+of+patterned+protein+samples.">Comparison of Bi(1), Bi(3) and C(60) primary ion sources for ToF-SIMS imaging of patterned protein samples.</a> Surface and Interface Analysis: SIA. 43 (1-2), 261-264 (2011).</li><li>Kozole, J., Winograd, N., Smentkowski, V. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cluster+Secondary+Ion+Mass+Spectrometry.">Cluster Secondary Ion Mass Spectrometry.</a> Surface Analysis and Techniques in Biology. , 71-98 (2014).</li><li>Tyler, B. J., Rayal, G., Castner, D. 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ToF-SIMS differentiates the ions according to their time of flight between two scintillators. The topography or sample roughness affects the flight time of the ions from different starting positions, which usually leads to a poor mass resolution with an increased width of peaks. Therefore, it is critical that the ROIs being analyzed are very flat, to ensure good signal collection8.
Another pitfall to avoid is charging. Since the Al-paint interface was fixed with the ins...

Al alloys have wide applications in engineering structures, such as in marine technology or military automotive, attributable to their high strength-to-weight ratio, excellent formability, and resistance to corrosion. However, localized corrosion of Al alloys is still a common phenomenon which affects their long-term reliability, durability, and integrity in various environmental conditions1. Paint coating is the most common means to prevent corrosion. Illustration of the corrosion developed at the interface between metal and paint coating can provide insights in determining the appropriate remedy for corrosion prevention.
The corrosion of Al alloys may take place via several different pathways. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) are two commonly applied surface microanalysis techniques in investigating corrosion. XPS can provide elemental mapping but not a holist molecular view of the surface chemical information2,3, while SEM/EDX provides morphological information and elemental mapping but with relatively low sensitivity.
ToF-SIMS is another surface tool for chemical mapping with high mass accuracy and lateral resolution. It has a low limit of detection (LOD) and is capable of revealing the distribution of the corrosion species formed at the metal-paint interface. Typically, SIMS mass resolution can reach 5,000-15,000, sufficient to differentiate the isobaric ions4. With its submicron spatial resolution, ToF-SIMS can chemically image and characterize the metal-paint interface. It provides not only morphological information but also the lateral distribution of molecular corrosion species at the top few nanometers of the surface. ToF-SIMS offers complementary information to XPS and SEM/EDX.
To demonstrate the capability of ToF-SIMS in surface characterization and imaging of the corrosion interface, two painted Al alloy (7075) coupons, one exposed to air only and one to a salt solution, are analyzed (Figure 1 and Figure 2). Understanding the corrosion behavior at the metal-paint interface exposed to the saline condition is critical to understand the performance of the Al alloy in a marine environment, for example. It is known that the formation of Al(OH)3 occurs during Al&#8217;s exposure to seawater5, but the study of Al corrosion still lacks comprehensive molecular identification of the corrosion and coating interface. In this study, the fragments of Al(OH)3, including Al oxides (e.g., Al3O5-) and oxyhydroxide species (e.g., Al3O6H2-), are observed and identified. The comparisons of SIMS mass spectra (Figure 3) and molecular images (Figure 4) of the negative ions Al3O5- and Al3O6H2- provide the molecular evidence of the corrosion products formed at the metal-paint interface of the salt solution-treated Al alloy coupon. SIMS offers the possibility to elucidate the complicated chemistry occurring at the metal-paint interface, which can help shed light on the efficacy of surface treatments in Al alloys. In this detailed protocol, we demonstrate this effective approach in probing the metal-paint interface to help new practitioners in corrosion research using ToF-SIMS.

<table border="0" cellpadding="0" cellspacing="0" style="width:737px;" width="737">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="41">
			<td height="41" style="height:41px;width:205px;">0.05 &#181;m Colloidal Silica polishing Solution</td>
			<td style="width:152px;">LECO</td>
			<td style="width:164px;">812-121-300</td>
			<td style="width:216px;">Final polishing solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">1 &#181;m polishing solution</td>
			<td style="width:152px;">Pace Technologies</td>
			<td style="width:164px;">PC-1001-GLB</td>
			<td style="width:216px;">Water based polishing solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">15 &#181;m polishing solution</td>
			<td style="width:152px;">Pace Technologies</td>
			<td style="width:164px;">PC-1015-GLBR</td>
			<td style="width:216px;">Water based polishing solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">3 &#181;m polishing solution</td>
			<td style="width:152px;">Pace Technologies</td>
			<td style="width:164px;">PC-1003-GLG</td>
			<td style="width:216px;">Water based polishing solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">6 &#181;m polishing solution</td>
			<td style="width:152px;">Pace Technologies</td>
			<td style="width:164px;">PC-1006-GLY</td>
			<td style="width:216px;">Water based polishing solution</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:205px;">Balance</td>
			<td style="width:152px;">Mettler Toledo</td>
			<td style="width:164px;">11106015</td>
			<td style="width:216px;">It is used for measuring the chemicals.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Epothin 2 epoxy hardener</td>
			<td style="width:152px;">Buehler</td>
			<td style="width:164px;">20-3442-064</td>
			<td style="width:216px;">Used for casting sample mounts</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Epothin 2 epoxy resin</td>
			<td style="width:152px;">Buehler</td>
			<td style="width:164px;">20-3440-128</td>
			<td style="width:216px;">Used for casting sample mounts</td>
		</tr>
		<tr height="56">
			<td height="56" style="height:56px;width:205px;">Fast protein liquid chromatography (FPLC) conductivity sensor</td>
			<td style="width:152px;">Amersham&#160;</td>
			<td style="width:164px;">AKTA FPLC</td>
			<td style="width:216px;">Used to measure the conductivity of the salt solution.</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:205px;">Final B pad</td>
			<td style="width:152px;">Allied</td>
			<td style="width:164px;">90-150-235</td>
			<td style="width:216px;">Used for 1 &#181;m and 0.05 &#181;m&#160; polishing steps</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">KCl&#160;</td>
			<td style="width:152px;">Sigma-Aldrich</td>
			<td style="width:164px;">P9333</td>
			<td style="width:216px;">Used to make the salt solution.</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:205px;">Low speed saw</td>
			<td style="width:152px;">Buehler Isomet</td>
			<td style="width:164px;">11-1280-160</td>
			<td style="width:216px;">Used to cut the Al coupons that are fixed in the epoxy resin.</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:205px;">MgCl2</td>
			<td style="width:152px;">Sigma-Aldrich</td>
			<td style="width:164px;">63042</td>
			<td style="width:216px;">Used to make the salt solution.</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:205px;">MgSO4</td>
			<td style="width:152px;">Sigma-Aldrich</td>
			<td style="width:164px;">M7506</td>
			<td style="width:216px;">It is used to make the salt solution.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">NaCl</td>
			<td style="width:152px;">Sigma-Aldrich</td>
			<td style="width:164px;">S7653</td>
			<td style="width:216px;">It is used to make the salt solution.</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:205px;">NaOH</td>
			<td style="width:152px;">Sigma-Aldrich</td>
			<td style="width:164px;">306576</td>
			<td style="width:216px;">It is used for adjusting pH of the salt solution.</td>
		</tr>
		<tr height="81">
			<td height="81" style="height:81px;width:205px;">Paint</td>
			<td style="width:152px;">Rust-Oleum&#160;</td>
			<td style="width:164px;">245217</td>
			<td style="width:216px;">Universal General Purpose Gloss Black Hammered Spray Paint. It is used to spray on the Al coupons.&#160;</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:205px;">Pan-W polishing pad</td>
			<td style="width:152px;">LECO</td>
			<td style="width:164px;">809-505</td>
			<td style="width:216px;">Used for 15, 6, and 3 &#181;m polishing steps</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:205px;">pH meter</td>
			<td style="width:152px;">Fisher Scientific</td>
			<td style="width:164px;">13-636-AP72</td>
			<td style="width:216px;">It is used for measuring the pH of the salt solution.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Pipette&#160;</td>
			<td style="width:152px;">Thermo Fisher&#160;</td>
			<td style="width:164px;">Scientific&#160;</td>
			<td style="width:216px;">Range: 10 to 1,000 &#181;L</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Pipette tip 1</td>
			<td style="width:152px;">Neptune&#160;</td>
			<td style="width:164px;">2112.96.BS&#160;</td>
			<td style="width:216px;">1,000 &#181;L</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Pipette tip 2</td>
			<td style="width:152px;">Rainin</td>
			<td style="width:164px;">17001865</td>
			<td style="width:216px;">20 &#181;L</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Silicon carbide paper</td>
			<td style="width:152px;">LECO</td>
			<td style="width:164px;">810-251-PRM</td>
			<td style="width:216px;">Grinding paper, 240 grit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Sputter coater</td>
			<td style="width:152px;">Cressington</td>
			<td style="width:164px;">108 sputter coater</td>
			<td style="width:216px;">It is used for coating the sample.&#160;&#160;</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:205px;">Tegramin-30 Semi-automatic polisher</td>
			<td style="width:152px;">Struers</td>
			<td style="width:164px;">6036127</td>
			<td style="width:216px;">Coarse/fine polishing/grinding</td>
		</tr>
		<tr height="54">
			<td height="54" style="height:54px;width:205px;">ToF-SIMS</td>
			<td style="width:152px;">IONTOF GmbH, M&#252;nster, Germany</td>
			<td style="width:164px;">ToF-SIMS V, equipped with Bi liquid metal ion gun and flood gun</td>
			<td style="width:216px;">It is used to acquire mass spectra and images of a specimen.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Vibromet 2 vibratory polisher</td>
			<td style="width:152px;">Buehler</td>
			<td style="width:164px;">67-1635-160</td>
			<td style="width:216px;">Final polishing step</td>
		</tr>
	</tbody>
</table>

imaging corrosion at the metal-paint interface using time-of-flight secondary ion mass spectrometry

Corrosion developed at the paint and aluminum (Al) metal-paint interface of an aluminum alloy is analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS), illustrating that SIMS is a suitable technique to study the chemical distribution at a metal-paint interface. The painted Al alloy coupons are immersed in a salt solution or exposed to air only. SIMS provides chemical mapping and 2D molecular imaging of the interface, allowing direct visualization of the morphology of the corrosion products formed at the metal-paint interface and mapping of the chemical after corrosion occurs. The experimental procedure of this method is presented to provide technical details to facilitate similar research and highlight pitfalls that may be encountered during such experiments.

Figure 3 presents the comparison of mass spectra between the metal-paint interface treated with salt solution and the interface exposed to air. The mass spectra of the two samples were acquired using a 25 kV Bi3+ ion beam scanning in 300 &#181;m x 300 &#181;m ROIs. The mass resolution (m/&#8710;m) of the salt solution-treated sample was approximately 5,600 at the peak of m/z- 26. The raw data of the mass spectra were exported after binning 10 channels. A grap...

Watch this Scientific Journal Video about Imaging Corrosion at the Metal-Paint Interface Using Time-of-Flight Secondary Ion Mass Spectrometry at JoVE.com

Imaging Corrosion at the Metal-Paint Interface Using Time-of-Flight Secondary Ion Mass Spectrometry

Time-of-flight secondary ion mass spectrometry is applied to demonstrate the chemical mapping and corrosion morphology at the metal-paint interface of an aluminum alloy after being exposed to a salt solution compared with a specimen exposed to air.

Corrosion developed at the paint and aluminum (Al) metal-paint interface of an aluminum alloy is analyzed using time-of-flight secondary ion mass ...

This approach reveals the corrosion process at the metal-paint interface, providing insight into mechanical and chemical changes at the interface with high surface sensitivity. Time-of-flight secondary ion mass spectrometry, or ToF-SIMS, is a powerful surface tool. It provides chemical maps with high lateral and mass resolution and allows effective characterization at the metal-paint interface.So an important tip that a new practitioner should know is to ensure that the sample does not touch the extraction cone to avoid potential damage to the instrument. The visual demonstration of this method is critical for researchers who are new to ToF-SIMS and will help them with the fundamental analysis process. To begin, load the prepared salt-exposed and air-exposed samples into the instrument load block.Pump down the load block, transfer the samples to the main chamber, and wait until the chamber is at or below 10 to the minus eight millibars. Then, power up the liquid metal ion gun, or LMIG, the analyzer, and the light source. Set the primary gun as LMIG with the preferred metal, bismuth, and start the LMIG using predefined spectrometry.Next, use either software or manual controls to move the sample stage to the Faraday cup. Then, auto-align the ion beam. After that, start measuring the target current at the Faraday cup, and select Direct Current.Click X Blanking, and adjust it until the target current is maximized. Then, repeat the process with Y Blanking. Stop the measurement when finished.Next, guided by the view through the main chamber window, slowly lower the sample stage until the top of the sample is lower than the bottom of the extractor cone. Then, position the stage under the cone so that the interface assembly is visible in the macro view in the software. After that, set the instrument to detect negative ions.Load the desired analyzer settings, and activate the analyzer. Next, switch to the micro scale view, and set the raster field of view to 300 by 300 micrometers. Then, set the signal to secondary ion, the raster size to 128 by 128 pixels, and the raster type to random.Adjust the secondary ion image of the ROI by slowly moving the sample stage vertically until the image is centered on the crosshair in the Navigator GUI. Do not move the joystick handle down too quickly while adjusting the Z direction, otherwise the extraction cone will hit the stage and get damaged. After that, use DC cleaning to remove the gold coating and surface contaminants.Once the sample surface is clean, enable charge compensation, and load the desired flood gun settings. Then, refocus the secondary ion image on the ROI. Once it is focused, increase the reflector voltage until the secondary ion image disappears.Then, decrease the voltage by 20 volts, and stop the adjustment. Next, open the mass spectrum in the imaging windows, and display the ROI of the metal-paint interface. Start a quick scan, and stop the scan once a spectrum appears.Then, in the mass spectrum window, select the known peaks in the mass spectrum from the quick scan, and fill in the formulas. After that, add the peaks of interest to the peak list. Open the measurement window, set the raster type to random, the size to 128 by 128 pixels, and the rate to one shot per pixel.Set the instrument to perform 60 scans, and begin the measurement. Save the completed spectrum afterwards. Then, name and save the ROI location.Move the stage to locate new ROIs to analyze. Next, load the desired high-resolution SIMS imaging settings for the LMIG. Move the sample stage to the Faraday cup, and realign and refocus the ion beam for imaging.Then, move the stage back to the saved ROI position. Adjust the reflector voltage, acquire a quick spectrum, and perform mass calibration. Then, set the raster type to random, the size to 256 by 256 pixels, and the rate to one shot per pixel.Set the number of scans to 150, and run the image acquisition. When finished, export the data, remove the sample, and shut down the instrument. Secondary ion mass spectrometry showed small aluminum oxide and oxyhydroxide peaks at the aluminum-paint interface of a sample exposed only to air, indicating mild corrosion.In contrast, a sample treated with salt water had much larger peaks and additional oxyhydroxide species. This was consistent with the salt water-treated sample having experienced more severe corrosion than the sample exposed only to air. 2D molecular images confirm that the aluminum oxide and oxyhydroxide species were much more prevalent in the sample that had been treated with salt water.Understanding surface damage and corrosion development is very challenging. ToF-SIMS is a perfect tool for this application, as illustrated in this procedure. In addition to studying the corrosion process, ToF-SIMS has been widely used in material surface characterization in radiological, biological, and environmental samples.Please be mindful that the settings of the mass spectra and image acquisition will vary depending on the types of the LMIG, remaining life of the LMIG, and other factors. We illustrate in this method that ToF-SIMS is very powerful in revealing the interfacial chemistry at the micro scale and providing chemical mapping with high lateral distribution and high mass accuracy. ToF-SIMS is a surface-sensitive technique.Please always wear gloves, and protect samples that you are handling.

Research

JoVE Journal

Chemistry

Matrix-assisted Laser Desorption/Ionization Time of Flight (MALDI-TOF) Mass Spectrometric Analysis of Intact Proteins Larger than 100 kDa

Matrix-assisted Laser Desorption/Ionization Time of Flight MALDI-TOF Mass Spectrometric Analysis of Intact Proteins Larger than 100 kDa

Effectively determining masses of proteins is critical to many biological studies (e.g. for structural biology investigations). Accurate mass ...

Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry

All cellular processes depend on the functionality of proteins. Although the functionality of a given protein is the direct consequence of its unique ...

A Study of the Complexation of Mercury(II) with Dicysteinyl Tetrapeptides by Electrospray Ionization Mass Spectrometry

A Study of the Complexation of MercuryII with Dicysteinyl Tetrapeptides by Electrospray Ionization Mass Spectrometry

In this study we evaluated a method for the characterization of complexes, formed in different relative ratios of mercury(II) to dicysteinyl tetrapeptide, ...

Rapid High-throughput Species Identification of Botanical Material Using Direct Analysis in Real Time High Resolution Mass Spectrometry

We demonstrate that direct analysis in real time-high resolution mass spectrometry can be used to produce mass spectral profiles of botanical material, ...

Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry

We demonstrate a versatile protocol to be used for determining the effectiveness of photocatalysts in degrading indoor air concentration (ppb) volatile ...

Real-time Breath Analysis by Using Secondary Nanoelectrospray Ionization Coupled to High Resolution Mass Spectrometry

Exhaled volatile organic compounds (VOCs) have aroused considerable interest, since they can serve as biomarkers for disease diagnosis and environmental ...

Synthesis and Mass Spectrometry Analysis of Oligo-peptoids

Peptoids are sequence-controlled peptide-mimicking oligomers consisting of N-alkylated glycine units. Among many potential applications, peptoids have ...

Characterization of Synthetic Polymers via Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) Mass Spectrometry

Characterization of Synthetic Polymers via Matrix Assisted Laser Desorption Ionization Time of Flight MALDI-TOF Mass Spectrometry

There are many techniques that can be employed in the characterization of synthetic homopolymers, but few provide as useful of information for end group ...

Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides