Utility Task Force Corrosion Pictures for IEEE C Fall 2018 & Submersible Transformer Galvanic Application Compatibility Chart (STGACC):

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1 Utility Task Force Corrosion Pictures for IEEE C Fall 2018 & Submersible Transformer Galvanic Application Compatibility Chart (STGACC): This report contains pictures of underground submersible transformer CTQ (Critical to Quality) components that are exposed to galvanic corrosion whereby causing possible water or chemical entry into an oil filled transformer s compartment via bolted flanges and handhole covers or screwed on fitting via taper pipe threads e.g. thermal wells, drain valves, tap changer covers etc. Equipment: 1 ph submersible Issue: Rusted holding clamp bolt Manufactured: 2010 (in service 5 years) : mild steel is the hardware silicon bronze, zinc plated, or stainless for bolt, washer, and nut Suggestion: Use 300 series stainless bolts and washers with 400 series nuts to prevent galling and galvanic corrosion for bolted bushings in service less 10 years Glen Falls NY Issue: Rusted tap changer pipe with bronze cap seized Manufactured: 2002 : tap changer head s threads are carbon steel, and cover is silicon bronze Equipment: 1-ph submersible Issue: Rusted bushing holding clamp and bolts cover protruding Manufactured: 2010 (in service 5 years) : mild steel is the hardware silicon bronze or stainless or both or are the bolts welded stainless or mild steel protruding from cover with stainless or silicon bronze hardware attached Suggestion: Use 300 series stainless tap changer head (refer to galvanic chart below for either being passive or active application) with silicon bronze cap or carbon steel tap changer head with 304 stainless caps Welded tap changer head should not corrode before cap Suggestion: Use 300 series stainless bolts and washers with 400 series nuts to prevent galling and galvanic corrosion for bolted bushings

2 Issue: Rusted pipe flange threads, silicon bronze sampler seized Manufactured: 2002 : pipe flange is carbon steel, sampler is silicon bronze stainless pipe plug on carbon steel pipe flange and Teflon tape barrier Issue: Rusted pipe flange threads, silicon bronze sampler seized Manufactured: Pending : pipe flange is carbon steel, sampler is silicon bronze stainless pipe plug on carbon steel pipe flange with Teflon tape barrier between different metals welded flange should not corrode before fitting and or sampling device service since for past 10 years see good example below Issue: Rusted pipe flange threads, sensor seized Manufactured: Pending : pipe flange is carbon steel, sensor is stainless is the sensor 316 or 304 refer to galvanic chart stainless pipe plug on carbon steel pipe flange flange should not corrode before sampling device in service since for past 10 years same as above

3 Issue: Rusted carbon steel pad for decal plate Manufactured: Pending : pad is carbon steel, plate decal is silicon bronze Suggestion: Use 300 series stainless plate decal and screw being of same material (refer to galvanic chart below for either being passive or active application) Issue: Rusted pipe nipple where drain valve is installed Manufactured: Pending : pipe nipple is carbon steel, drain valve is silicon bronze Issue: Rusted nipple where drain valve is installed Manufactured: 2013 Application: Sludge/High Polluted : pipe nipple is carbon steel, drain valve and pipe plug is silicon bronze Issue: Galvanic corrosion all over tank and cover + leaking drain valve drain valve is brass (or equivalent), had leaks at the fitting with the tank or the pipe between the 2. Drain valve eliminated since few years and replaced with a plug on top of cover Manufactured: 8 years in service; primer with powder top coat and Devtar (asphalt) on bottom of tank about 1 foot high Installed: Canada Northeast Removed: N/A Application: dry vaults or with little drainage water but many covered with water for some time stainless globe valve on carbon steel pipe flange (refer to galvanic chart below for either being passive or active application) and silicon bronze globe valve on stainless steel pipe nipple should not have corroded before valve no tank welded components should corrode first. stainless globe valve on carbon steel pipe flange and silicon bronze globe valve on stainless steel pipe nipple should not have corroded before valve no tank welded components should corrode first. Suggestion: Use some epoxy coatings with zinc rich primer which are superior for underground applications. Use 304 stainless globe valve on carbon steel pipe flange and silicon bronze globe valve on stainless steel (continues next page)

4 : copper bearing steel tank and cover; no external accessories such as PRV, sight gage, thermometer; surrounded with bare copper grounding wire which accelerate galvanic corrosion on the tank Was the water in the vault stagnant and/or salty? What are the effects of Devtar (asphalt) in an aqueous salty solution does it affect the PH accelerating other types of corrosion e.g. pitting, chemical, bacterial, etc. Issue: Rust or other corrosion showing where the terminals were bolted to tin plated neutral Manufactured: 2013 Installed: 2013 : tin plated copper neutral was the connecting terminal tin plated Issue: None: No Rust showing where terminal was bolted to tin plated neutral Manufactured: 2015 Installed: 2016 : tin plated copper neutral, shows a tin plated 2-hole terminal lead

5 Issue: Rusted pipe flange threads, pipe plug possibly seized Manufactured: 2009 Installed: 2009 : pipe flange is carbon steel, pipe plug is silicon bronze stainless pipe plug on carbon steel pipe flange tank welded flange should not corrode before sampling device Equipment: 1-ph submersible Issue: None: No galvanic corrosion where dissimilar metals touching; only rusting at tank bottom Manufactured: 2009; powder coat Installed: Fossil Creek, Colorado ; no maintenance Application: Salt Water chloride : tank material mild steel with welded stainless nut provision and tin-plated bronze terminal; fitting barrier Teflon tape Equipment: 1-ph submersible Issue: Same as 1024 Fossil Creek only rusting at tank bottom Manufactured: 2001; powder coat Installed: Autumn Ridge, Colorado Removed: 2012; no maintenance Application: Salt Water chloride : tank material mild steel; unsure if fitting had Teflon tape as a barrier Equipment: 1-ph submersible Issue: None: No galvanic corrosion where dissimilar metals touching Manufactured: 1992; powder coat Installed: Alameda St. Colorado ; no maintenance Application: Salt Water : tank material mild steel with welded stainless nut provision and tin-plated bronze terminal; fitting barrier Teflon tape Perfect Recommendation: if user wants to continue to use bronze valves, terminals, etc. and/or there s no stainless version of those terminals or components that exist on the market. A copper bearing steel tank with welded stainless provision and tin-plated bronze terminals all having fitting barriers with Teflon tape Perfect Recommendation: if user wants to continue to use bronze valves, terminals, etc. and/or there s no stainless version of those terminals or components that exist on the market. A copper bearing steel tank with welded stainless provision and tin-plated bronze terminals all having fitting barriers with Teflon tape

6 Issue: Rust showing where terminals were bolted to neutral Manufactured: 2009 Installed: 2009 : copper neutral Was the neutral blade tin plated, was the connecting terminal tin plated, and what type of hardware was used Issue: Sever pitting of the temperature gauge s aluminum housing Manufactured: 2009 Installed: 2013 : Aluminum housing with stainless steel screws on faceplate with brass/silicon bronze or brass thermal well as part of assembly; thermal well screwed into welded steel tank pipe flange. Suggestion: Use stainless housing with stainless thermal well instead of aluminum with silicon bronze or brass thermal well screwing onto carbon steel tank pipe flange Issue: paint degradation flaking of the temperature gauge aluminum housing; severe rusting around pipe flange Manufactured: 2000 Installed: 2002 : Aluminum housing with stainless steel screws on faceplate with brass/silicon bronze or brass thermal well as part of assembly; thermal well screwed into welded steel tank pipe flange. Suggestion: Use stainless housing with stainless thermal well instead of aluminum with silicon bronze or brass thermal well screwing onto carbon steel tank pipe flange

7 Issue: Rusted pipe flange threads, pipe plug and sampler possibly seized Manufactured: 2001 Installed: 2002 : pipe flanges are carbon steel; pipe plug and sampler are silicon bronze stainless pipe plug on carbon steel pipe flange tank welded flange should not corrode before sampling device Issue: Sever pitting of the temperature gauge aluminum housing Manufactured: 2013 Installed: 2013 Application: Sludge/High Polluted : Aluminum housing with stainless steel screws on faceplate with brass/silicon bronze or brass thermal well as part of assembly; thermal well screwed into welded steel tank pipe flange. Suggestion: Use stainless housing with stainless thermal well instead of aluminum with silicon bronze or brass thermal well screwing onto carbon steel tank pipe flange

8 Issue: Sever pitting of the temperature gauge aluminum housing Manufactured: 2015 Installed: 2015 Application: Sludge/High Polluted : Aluminum housing with stainless steel screws on faceplate with brass/silicon bronze or brass thermal well as part of assembly; thermal well screwed into welded steel tank pipe flange Suggestion: Use stainless housing with stainless thermal well instead of aluminum with silicon bronze or brass thermal well screwing onto carbon steel tank pipe flange Issue: Rusted parking stands near hardware connection, bolts possibly seized Manufactured: 2009 Installed: 2009 Application: Sludge/High Polluted : parking stands are carbon steel; is the hardware silicon bronze, zinc plated, 316, or 304 stainless washers and bolts with 400 series nuts instead of zinc plated steel or silicon bronze on carbon steel Issue: Rusted parking stands near hardware connection, bolts possibly seized Manufactured: 2012 Application: Sludge/High Polluted : parking stands are carbon steel; is the hardware silicon bronze, zinc plated, 316, or 304 stainless washers and bolts with 400 series nuts instead of zinc plated steel or silicon bronze on carbon steel

9 Issue: Rusted ground flange assembly with bronze padlock, handle, lever, and shaft Manufactured: 2006 Installed: 2006 Application: Sludge/High Polluted : grounding welded assembly is carbon steel; padlock, lever, and shaft are bronze Suggestion: Use stainless ground flange assembly instead of carbon steel when paring with silicon bronze padlock, lever, and shaft (refer to galvanic chart below for either being passive or active application) Corrosion on tank below Devtar line. Corrosion on cooling radiator fin below Devtar line Equipment: 167kVA submersible Issue: drain valve is brass (or equivalent), had leaks at the fitting with the tank or the pipe between the 2. Drain valve eliminated since few years and replaced with a plug on top of cover Manufactured: 2004; e-coat and Devtar (asphalt) on bottom tank about 1 foot high Installed: Canada Northeast Removed: 2009 Application: dry vaults or with little drainage water but many covered with water for some time : copper bearing steel tank and cover; no external accessories such as PRV, sight gage, thermometer; surrounded with bare copper grounding wire which accelerate galvanic corrosion on the tank Was the water in the vault stagnant and/or salty? What are the effects of Devtar (asphalt) in an aqueous salty solution does it affect the PH accelerating other types of corrosion e.g. pitting, chemical, bacterial, etc. Suggestion: Suggestion: Use some epoxy coatings with zinc rich primer which are superior for underground applications No corrosion at tank grounding pad.

10 Issue: galvanic corrosion where dissimilar metals touching silicon bronze or brass thermal well screw into welded steel pipe flange Manufactured: 2005; 3mils of zincrich primer with 3mils of black epoxy finish top coat Installed: Boston, Massachusetts Northeast Removed: 2017 : tank flange material steel with silicon bronze or brass thermal well, padlock, pipe plug, and drain valve Suggestion: if user wants to continue to use bronze valves, terminals, etc. and/or there s no stainless version of those terminals or component that exist on the market. A copper bearing steel tank with welded stainless provision and tin-plated bronze terminals all having fitting barriers Teflon tape Another suggestion maybe thermal well, padlock, pipe plug, and drain valve being 304 stainless on welded steel pipe flange and nipple Issue: slight galvanic corrosion where dissimilar metals touching on parking stands Manufactured: 2005; 3mils of zincrich primer with 3mils of black epoxy finish top coat Installed: New England Northeast Removed: 2017 : tank material copper bearing steel

11 Issue: None: No rust around stainless bolt and washer in carbon steel cover weld nut Manufactured: 2013 Application: Not Coastal : carbon steel welded nut, bolt and washer hardware are stainless is the hardware 316 or 304 Issue: None: No rust around stainless bolt and washer in carbon steel cover weld nut Manufactured: 2006 Application: Not Coastal, ATL : pipe flange is carbon steel, bolt and washer hardware are stainless is the hardware 316 or 304 Issue: slight rust on tap changer threads having bronze cap Manufactured: 2006 Application: Not Coastal, ATL : what are the tap changer thread s material if stainless, was it cleaned or brushed with carbon steel Issue: Rusted network protector Manufactured: This one was in service at 2 locations in For the second installation, the last 10 years Application: in Providence Rhode Island at a transit station; sidewalk area that is typically heavily treated with salt in the winter time for foot traffic. : protector is carbon steel what are the paint requirements and did heating escalate the galvanic corrosion process Suggestion: Did protector have adequate radiation needed for the protector housing ensure test data was provided along with paint maps; temperature can accelerate galvanic corrosion Use some epoxy coatings with zinc rich primer which are superior for underground applications.

12 Submersible Transformer Galvanic Application Compatibility Chart (STGACC) Tank Misc. External Hardware (e.g. Bolts, nuts, washers) Valves and Gauges Screw on Fittings Plugs and Caps Bushing Flanges Parking Stands Copper Bearing Steel (Low Alloy Steel) (.35V) Tank will 304 (.55V) & 316 (.58V) (.35V) Tank will 304 (.55V) & 316 (.58V) (.35V) Tank will 304 (.55V) & 316 (.58V) (.35V) Tank will 304 (.55V) & 316 (.58V) 316 (.23V) Tank will 304 (.55V) & 316 (.58V) Tank will Same as Tank 304 (.13V) (stagnant 304 (.13V) (stagnant 304 (.13V) (stagnant 304 (.13V) (stagnant 304 (.13V) (stagnant (.2V) External Hardware will Threshold Not- (.2V) Valves and Gauges will Threshold Not- (.2V) Screw on Fittings will Threshold Not- (.2V) Plug and Caps will Threshold Not- 316 (.32V) Flange will 304 (Passive) (.42V) (stagnant External Hardware will (.42V) (stagnant Valves and Gauges will (.42V) (stagnant Screw on Fittings will (.42V) (stagnant Plug and Caps will corrode Not- 304 (OV) same as tank material Same as Tank 430 (.17V) 430 (.17V) 430 (.17V) 430 (.17V) 316 (.03V)

13 (.22V) Tank will (.22V) Tank will (.22V) Tank will (.22V) Tank will 316 (.45V) Tank will 304 (stagnant (.25V) Non- Tank will (.25V) Non- Tank will (.25V) Non- Tank will (.25V) Non- Tank will 304 (OV) same as tank material (stagnant Same as Tank 430 (0V) 430 (0V) 430 (0V) 430 (0V) 316 (.1V) 316 (Passive) (.23V) External Hardware will (.45V) (stagnant External Hardware will 430 (.2V) External Hardware will Threshold Not- (.23V) Valves and Gauges will (.45V) (stagnant Valves and Gauges will 430 (.2V) Valves and Gauges will Threshold Not- (.23V) Screw on Fittings will (.45V) (stagnant Screw on Fittings will 430 (.2V) Screw on Fittings will Threshold Not- (.23V) Plug and Caps will (.45V) (stagnant Plug and Caps will corrode Not- 430 (.2V) Plug and Caps will corrode Maybe Threshold Not- 304 (.45V) Flange will 316 (OV) same as tank material 304 (.03V) Same as Tank

14 316 (stagnant (.12V) (.15V) Non- 430 (.1V) (.12V) (.15V) Non- 430 (.1V) (.12V) (.15V) Non- 430 (.1V) (.12V) (.15V) Non- 430 (.1V) 304 (.32V) Tank will 316 (OV) same as tank material (stagnant 304 (.1V) Same as Tank 409 Non- (Passive) (.02V) 304 (.22V) & 316 (.25V) 304 (.2V) & 316 (.1V) External Hardware will Threshold Not (.02V) 304 (.22V) & 316 (.25V) 304 (.2V) & 316 (.1V) Valves and Gauges will Threshold Not (.02V) 304 (.22V) & 316 (.25V) 304 (.2V) & 316 (.1V) Screw on Fittings will Threshold Not (.02V) 304 (.22V) & 316 (.25V) 304 (.2V) & 316 (.1V) Plug and Caps will Threshold Not 409 (OV) same as tank material Non- 304 (.2V) & 316 (.1V) Flange will Threshold Not Same as Tank

15 409 (stagnant (.22V) Tank will 304 (.42V) & 316 (.45V) 304 (0V) & 316 (.1V) (.22V) Tank will 304 (.42V) & 316 (.45V) 304 (0V) & 316 (.1V) (.22V) Tank will 304 (.42V) & 316 (.45V) 304 (0V) & 316 (.1V) (.22V) Tank will 304 (.42V) & 316 (.45V) 304 (0V) & 316 (.1V) 409 (OV) same as tank material (stagnant 304 (0V) & 316 (.1V) Same as Tank Copper Bearing Steel (Low Alloy Steel) ~ -.63 ~ ~ ~ ~ ~ ~ ~ ~ ~ -.4 Reference:

16 Below shows the galvanic series measured in seawater for some common metals and alloys. When two metals are further apart in the list (e.g. a larger difference between the two numbers), the driving force for galvanic corrosion is increased. The most anodic (active) metals are at the top and most cathodic (noble) at the bottom. Both solid and hollow bars are shown for the stainless steels. The hollow bars represent actively corroding stainless steel, which has a different potential then passive (not corroding) stainless steel. In most applications, where dissimilar metals are combined, the passive (solid) bar should be used to determine the position of the stainless steel.

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