An Analysis of Corrosion Performance for a variety of Substrates and Coatings David A. Smith, Marty Higgins, Gary Barone Restek Corporation Dr. Bruce Kendall Elvac Laboratories Base Material Cost Comparison 3000 250 2500 200 2000 1500 $USD $USD 150 1/4" Tee 100' 1/4" Tubing 100 1000 50 500 0 0 316 SS HP Alloy 1 Outline Cost vs. effective solution (coatings) Coating process Coating data Corrosion resistance data Water/drydown performance Other Applications Chemical Vapor Deposition Process Thermal decomposition of silanes Amorphous silicon deposition Functionalization of surface if desired Process Surface preparation (caustic, aqueous) Vacuum 400º 400ºC Applied in vessel or oven chamber Total 3D coverage, not line-of-sight Tubing, fittings, frits, fine structure 2 Coating Cross Section Silcosteel GD-OES Depth Profile 3 Secondary Enhancements Amorphous silicon deposition Up to 20um in depth Multiple layers to eliminate pinpin-holes Enhances corrosion resistance Additional organic functionalization possible Decrease of pinpin-holes Improving surface inertness Patented Functionalization amorphous silicon (a-Si) FS Capillary FS Capillary 4 Coating Appearances Coating Appearances (cont.) 5 Corrosion Resistance Stainless steel surfaces susceptible to attack from hydrochloric acid, sulfuric acid and nitric acid Is it possible to Enhance Corrosion resistance by deposition of an amorphous silicon layer? Silicon is insoluble in hydrochloric acid, sulfuric acid and nitric acid 6M HCl Data Tubing Type Average Weight loss (g) Mpy corrosion / Standard dev. 316 welded 0.3085 29.94 / 0.98 CR 316 welded 0.0492 4.76 / 4.45 1.9 EP 316 seamless 0.1669 15.57 / 1.09 1.0 CR EP 316 0.0019 0.17 / 0.06 97.2 CR/Func CR/Func.. EP 316 0.0031 0.29 / 0.03 54.6 HP Alloy 0.0075 0.67 / 0.05 23.2 Enhancement 72 hr exposure, agitation every 8hrs 22º 22ºC n=3 for each 6 Corrosion Resistant Data (cont.) External Evaluation Certified corrosion engineers Spectroscopic analysis Pitting corrosion Electrochemical Cyclic Polarization in neutral, acidic, alkaline Atmospheric corrosion ASTM moisture condensation Salt spray ASTM B117 Stress corrosion cracking (MgCl2; ASTM G36) Corrosion Data ASTM G45 Method B ASTM G45 method B; Pitting and Crevice Corrosion 6% Ferric Chloride solution 72hrs, 20º 20ºC Gasket wrap Sample Initial Weight (g) Final Weight (g) Weight Loss (g) Weight Loss (g/m2) aSi Coated Sample 17 10.4105 10.3710 0.0395 19 aSi Coated Sample 28 10.1256 10.0743 0.0513 25 aSi Coated Sample 47 10.1263 10.0742 0.0521 25 Bare Sample 27 10.0444 9.5655 0.4789 231 Bare Sample 34 10.1265 9.6923 0.4342 209 Bare Sample 37 10.1007 9.6276 0.4731 228 7 ASTM G45 B (cont.) Bare 316L Stainless Steel coupon showing severe crevice corrosion ASTM G45 B (cont.) Corrosion resistant treated sample showing no crevice corrosion only slight pitting corrosion 8 Corrosion Data ASTM G61 ASTM GG-61; Cyclic Polarization Electrochemical Corrosion Testing Acid, neutral, basic aqueous solutions with varying Cl- ion concentrations (100, 3000, 5000ppm) EG&G VersaStat System, 23º 23ºC 316L vs. Silcosteel®-CR on 316L, 304L Neutral solution; 3000ppm Cl- -CR vs 316L Raw: 50x improvement Sample Ec, mV Ic, uA/cm^2 Eb, mV CR, mpy 316 L -418 0.096 370 0.04 aSi Coated 316 L -533 0.002 1460 0.0009 304 L -435 0.145 361 0.06 Ec = corrosion potential Ic = current density at Ec Eb = pitting potential CR = corrosion rate ASTM G61 (cont.) Acidic Solution; 1N H2SO4; 3000ppm Cl- -CR vs 316L Raw: 10x improvement Sample Ec, mV Ic, uA/cm^2 Eb, mV CR, mpy 316 L -662 1.920 370 0.83 aSi Coated 316 L -843 0.123 927 0.05 304 L -639 2.650 587 1.14 9 Corrosion Data ASTM B117 ASTM B 117 – “Practice for Operating Salt Spray (Fog) Apparatus.” 1000 hour exposure 100 degree Fahrenheit 3.5% by weight sodium chloride Reproduces exposure to marine environments. ASTM B117 (cont.) Amorphous silicon treated samples showed no signs of bleeding, rusting, or pitting corrosion 10 ASTM B117 (cont.) The nonnon-treated samples showed some light surface rusting, but no signs of pitting corrosion. Corrosion Data ASTM D4585 ASTM D 4585, “Practice for Testing the Water Resistance of Coatings Using Controlled Condensation.” 1000 hour study 100 degrees Fahrenheit Distilled water Reproduces exposure to atmospheric conditions 11 ASTM D4585 (cont.) Amorphous silicon treated samples showed no signs of bleeding, rusting, or pitting corrosion ASTM D4585 (cont.) A light surface oxide film was seen on the bare samples. 12 Benefits To extend lifetimes of equipment exposed to corrosive environments and/or process streams Longer PM cycles minimal cost increase Protection of high value equipment in corrosive environments Known Applications Enhancing corrosion resistance in Marine environments Process streams containing HCl Protection of Continuous Emissions Monitoring Equipment (Nitric and Sulfuric acid) Use in Automotive Exhaust test equipment (Nitric and Sulfuric acid) 13 Effect of moisture Coatings decrease adsorption of water, hydrophobic Leads to quicker removal of moisture through sampling lines Components less susceptible to corrosion Faster cycle times and increased accuracy with less moisture hold-up in tubing Several coatings and surfaces available Moisture Data Amount of time to equilibrate a 1ppm moisture sample through 100 feet of dry tubing: Commercial Seamless 316L tubing: 180 minutes (96% equilibrated) Electropolished Seamless 316L tubing: 60 minutes (98% equilibrated) a-silicon coated ee-polished seamless 316L tubing 30 minutes (98% equilibrated) 14 Moisture Data (cont) Time to dry 100’ tubing wetted with 1ppm of moisture when connected to a dry purge Commercial Seamless 316L tubing: 175 minutes Electropolished Seamless 316L tubing: 65 minutes a-silicon coated ee-polished seamless 316L tubing 35 minutes Additional Benefits of a-silicon layer Inertness: Coating is non-reactive to organic compounds Transfer lines Instrumentation parts GC consumables Anti-Coking. Coating barrier eliminates catalytic effect of substrate. Ultra-High-Vacuum (UHV). Reduces outgassing of vacuum components. 15 Cost Comparison 250 3000 2500 200 2000 1500 $USD $USD 150 1/4" Tee 100' 1/4" Tubing 100 1000 50 500 0 0 316 SS CR 316 SS HP Alloy 16 Conclusions/Future Develop Corrosion data comparing coating on different substrates Enhancement of Carbon Steel Protection of high nickel alloys Value of coating in marine environments Application of coating to valves & fasteners Continual process improvement and new product development Hardness Improved corrosion resistance Customized surfaces Acknowledgements Swagelok Company O’Brien Corporation Haritec Scientific & Engineering Support Matco Associates ® 17