1. Atmospheric Corrosion Testing Comparison of Electrodeposited Hard Chrome to HVOF WC/17Co and Tribaloy 400 Three-Year Atmospheric Exposure Exposures Conducted at Naval Research Laboratory Marine Corrosion Test Facility, Key West, FL Report Prepared by Paul Natishan and Bruce Sartwell Naval Research Laboratory

2. Atmospheric Corrosion Testing Substrate Materials: 4340 steel and 7075-T73 aluminum alloy Substrate Preparation:For EHC, grit blast with 180-220 grit Al 2 O 3 For HVOF, grit blast with 54 grit Al 2 O 3 Coating Deposition: EHC deposited at NADEP Jacksonville following MIL-STD-1501; on 7075 alloy, 0.0015-inch-thick sulfamate Ni deposited prior to Cr WC/17Co deposited at NADEP Jacksonville using hybrid Diamondjet gun, hydrogen fuel, Diamalloy 2005 powder Tribaloy 400 deposited at Southwest Aeroservice using Jet Kote II, hydrogen fuel, Stellite T-400 powder Coating thicknesses of 0.004 inches Tested as-deposited (no grinding) Epoxy masking used on non-coated surfaces

3. HVOF and Hard Chrome Coatings on 4340 Steel Atmospheric Exposure For 3 Years Before Cleaning

4. HVOF and Hard Chrome Coatings on 4340 Steel Atmospheric Exposure For 3 Years After Cleaning

5. HVOF and Hard Chrome Coatings on 4340 Steel Atmospheric Exposure For 3 Years Before Cleaning

6. HVOF and Hard Chrome Coatings on 4340 Steel Atmospheric Exposure For 3 Years After Cleaning

8. HVOF and Hard Chrome on 7075 Aluminum Atmospheric Exposure for 3 Years Before Cleaning Pits

9. HVOF and Hard Chrome on 7075 Aluminum Atmospheric Exposure For 3 Years After Cleaning Pits

10. HVOF and Hard Chrome on 7075 Aluminum Atmospheric Exposure for 3 Years Before Cleaning Pits

11. HVOF and Hard Chrome on 7075 Aluminum Atmospheric Exposure For 3 Years After Cleaning Pits

12. HVOF and Hard Chrome on 7075 Aluminum Atmospheric Exposure For 3 Years After Cleaning Pits

14. Summary 1. On 4340 steel, the HVOF WC/Co coating outperformed the EHC and HVOF T-400 coatings. 2. On 7075 aluminum, in general the EHC coating performed best. 3. On 7075 aluminum, two samples of a smaller dimension (3 x 4 inches) had protection ratings that were better than the EHC coatings on the 4 x 6 inch samples. 4. Some general corrosion of the WC/Co coatings was observed.