Grantee Research Project Results
2007 Progress Report: Magnesium Rich Coatings for Corrosion Control of Reactive Metal Alloys
EPA Grant Number: X832541C006Subproject: this is subproject number 006 , established and managed by the Center Director under grant X832541
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for Environmental and Energy Research (CEER)
Center Director: Earl, David A.
Title: Magnesium Rich Coatings for Corrosion Control of Reactive Metal Alloys
Investigators: DeRosa, Rebecca
Institution: Alfred University
EPA Project Officer: Aja, Hayley
Project Period: January 1, 2007 through August 1, 2008
Project Period Covered by this Report: January 1, 2007 through August 1, 2008
RFA: Targeted Research Center (2006) Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research
Objective:
We are testing magnesium rich coating (MRC) systems as possible chromate replacement coatings for corrosion control of reactive metal alloys. The hypothesis is that the Mg particles embedded in an inorganic or organic matrix coating will sacrificially corrode and provide extended corrosion protection to the underlying metal substrate. Our goal is to understand the role of the Mg particles as sacrificial anodes in MRC’s on aluminum 2024 and 7075 in a corrosive environment. We are currently using electrochemical techniques including electrochemical impedance spectroscopy (EIS), d.c. polarization, and open circuit potential (OCP) monitoring to determine the reliability of the coatings as corrosion inhibitors. In addition, we are also using scanning electron microscopy (SEM), electron probe x-ray microanalysis (EPMA), and x-ray photoelectron spectroscopy (XPS) to determine the state of the magnesium particles.
Progress Summary:
We have received six different primer systems to date from North Dakota State University (NDSU): two separate organic coatings (CPM 1040 & Akzo) on Al-2024 and Al-7075 panels, and one inorganic coating (SMT 30) on Al-2024 and Al-7075 panels.
Panels from each system were cut into 1.5”x 2.5” sections. A glass cylinder was clamped to each section exposing a surface area of 7.06 cm2. The glass cylinder was then filled with dilute Harrison’s solution (DHS), consisting of 0.35wt% (NH4)2SO4 and 0.05wt% NaCl in distilled water (ph=5.4). DHS was chosen because it mimics acid rain which has shown to cause pitting corrosion when exposed to bare aluminum. A saturated calomel electrode was used as the reference electrode and a platinum wire was used as the counter electrode. A Solartron 1260 potentiostat/galvanostat with a 1287 frequency response analyzer and dedicated EIS Zplot and Zview software were used to collect and analyze electrochemical impedance and OCP data. The impedance spectra were collected at a rate of 10 points per decade using the frequency range of 10 kHz to 0.1 Hz. The applied AC sinusoidal amplitude was 10 mV applied at the open circuit potential for all systems. Electrochemical impedance analysis consisted of measuring the initial OCP for the system followed by EIS analysis versus exposure time over a period of 25+ days. Samples were removed from exposure based on changes in impedance modulus intensity.
Coating thickness was determined using an Elcometer 345 under non-ferrous conditions. At least 10 points were measured for each sample area (exposed versus unexposed regions).
The elemental composition of the coating surfaces was determined using XPS. Measurements were carried out at 13 μPa with a PHI Quantera SXM equipped with an Al Kα (1486.6 eV) source. The XPS was calibrated to + 0.1 eV using Ag (3d) line at 368.3 eV. The system linearity was calibrated within + 0.1 eV of the difference between Cu (2p) at 932.7 eV and Au (4f7/2) at 84.0 eV. Charging of the surface was prevented using an electron neutralizer at 1 V and 20 μA. A take-off angle of 45° was used in all scans. High resolution scans for C(1s), O(1s), Mg(2p), Al(2p), Na(2p), Cl(2p), and Cu(2p) were collected using a 200 μm beam size at 41 W and 15 kV. An additional high resolution scan of Si(2p) was also performed on the inorganic systems. Sputter depth profiling was accomplished through the following schedule using Ar+: 1 minute at 3 kV 3x3 mm for one cycle and 2 minutes at 5 kV 3x3 mm for 5 cycles. Compositional identification and atomic concentrations were determined with MultiPak 8 (Version 8.0, Ulvac-Phi, Inc.).
For SEM and EPMA imaging, a cross section of the panel was mounted in a jet set two part epoxy. After cure the sample was leveled using 400 grit followed by 600 grit SiC sandpaper. The sample was inspected optically between each step to check for coating pullout and even grinding. Hand fine polishing was carried out using 9 μm, 3 μm, and 1 μm diamond paste followed by 0.05 μm Al2O3 until mirror finish. Images were taken using an FEI Co. Mod. Quanta 200F environmental scanning electron microscope (ESEM) equipped with field emission gun. The electron source is a tungsten filament. The chamber was held in high vacuum mode at 13.3 mPa. The accelerating voltage is at 20 keV. Backscattered images were taken at a working distance of 9.8 mm.
Future Activities:
Complete crosshatched exposures in 90% relative humidity for all systems. Fully evaluate crosshatched samples and compare results to DHS exposures. Experiment with plasma pretreatment and compare results to previous exposures.
Journal Articles:
No journal articles submitted with this report: View all 2 publications for this subprojectSupplemental Keywords:
corrosion, metal rich coating, magnesium rich coating, aluminum alloy, magnesium alloy,Relevant Websites:
http://www.estcp.org/Technology/WP-0731-FS.cfm Exit
http://www.ndsu.nodak.edu/research/article.php?article_number=75 Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
X832541 Center for Environmental and Energy Research (CEER) Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
X832541C001 Microarray System for Contaminated Water Analysis
X832541C003 The Fining Behavior of Selectively Batched Commercial Glasses
X832541C004 The Use of Fly Ash in the Production of SiAlON based Structural Ceramics
X832541C005 Separation and Purification of Hydrogen From Mixed Gas Streams Using Hollow Glass Microspheres
X832541C006 Magnesium Rich Coatings for Corrosion Control of Reactive Metal Alloys
X832541C008 Tunneled Titanate Photocatalysts for Environmental Remediation and Hydrogen Generation
X832541C009 Material and Environmental Sustainability in Ceramic Processing
X832541C010 Robust, Spectrally Selective Ceramic Coatings for Recycled Solar Power Tubes
X832541C011 Recycling of Silicon-Wafers Production Wastes to SiAlON Based Ceramics with Improved Mechanical Properties
X832541C012 Emissions Reduction of Commercial Glassmaking Using Selective Batching
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
Main Center: X832541
10 publications for this center
2 journal articles for this center