c57.12.24 galvanic corrosion task force fall 2018 rev 09...

Utility Task Force Corrosion Pictures for IEEE C57.12.24 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)

Material: 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

Equipment: 3-ph submersible

Issue: Rusted tap changer pipe

with bronze cap seized

Manufactured: 2002

Material: tap changer head’s

threads are carbon steel, and

cover is silicon bronze


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


Issue: Rusted bushing holding

clamp and bolts cover protruding

Manufactured: 2010 (in service 5

years)

Material: 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


stainless bolts and washers

with 400 series nuts to

prevent galling and

galvanic corrosion for

bolted bushings


Issue: Rusted pipe flange threads,

silicon bronze sampler seized

Manufactured: 2002

Material: pipe flange is carbon

steel, sampler is silicon bronze

Suggestion: Use 304

stainless pipe plug on

carbon steel pipe flange

and Teflon tape barrier



silicon bronze sampler seized

Manufactured: Pending


steel, sampler is silicon bronze

Suggestion: Use 304



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



sensor seized



steel, sensor is stainless is the

sensor 316 or 304… refer to

galvanic chart

Suggestion: Use 304


carbon steel pipe flange…

flange should not corrode

before sampling device

in service since for past 10

years same as above


Issue: Rusted carbon steel pad for

decal plate


Material: pad is carbon steel, plate

decal is silicon bronze


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


Material: pipe nipple is carbon

steel, drain valve is silicon bronze

Suggestion: Use 304

stainless globe valve on


(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.


Issue: Rusted nipple where drain

valve is installed

Manufactured: 2013

Application: Sludge/High Polluted

Material: pipe nipple is carbon

steel, drain valve and pipe plug is

silicon bronze

Suggestion: Use 304



and silicon bronze globe

valve on stainless steel…

pipe nipple should not

have corroded before

valve… no tank welded

components should

corrode first.


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

Suggestion: Use some

epoxy coatings with zinc

rich primer which are

superior for underground

applications. Use 304



and silicon bronze globe

valve on stainless steel

(continues next page)

Material: 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

Removed: 2018

Application: Coastal

Material: 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

Removed: 2018


Material: tin plated copper

neutral, shows a tin plated 2-hole

terminal lead



pipe plug possibly seized

Manufactured: 2009

Installed: 2009

Removed: 2018



steel, pipe plug is silicon bronze

Suggestion: Use 304



tank welded flange should

not corrode before

sampling device


Issue: None: No galvanic corrosion

where dissimilar metals touching;

only rusting at tank bottom

Manufactured: 2009; powder coat

Installed: 2011 1024 Fossil Creek,

Colorado

Removed: 2018; no maintenance

Application: Salt Water chloride

Material: 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


Issue: Same as 1024 Fossil Creek

only rusting at tank bottom


Installed: 2002 6802 Autumn

Ridge, Colorado


Application: Salt Water chloride

Material: tank material mild steel;

unsure if fitting had Teflon tape as

a barrier


Issue: None: No galvanic corrosion

where dissimilar metals touching


Installed: 1993 1213 Alameda St.

Colorado


Application: Salt Water

Material: 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





barriers with Teflon tape


Issue: Rust showing where

terminals were bolted to neutral

Manufactured: 2009

Installed: 2009

Removed: 2018


Material: 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

Removed: 2018


Material: 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

Removed: 2018

















pipe plug and sampler possibly

seized

Manufactured: 2001

Installed: 2002

Removed: 2018


Material: pipe flanges are carbon

steel; pipe plug and sampler are

silicon bronze

Suggestion: Use 304



tank welded flange should

not corrode before

sampling device



temperature gauge aluminum

housing

Manufactured: 2013

Installed: 2013

Removed: 2018

















temperature gauge aluminum

housing

Manufactured: 2015

Installed: 2015

Removed: 2018
















Issue: Rusted parking stands near

hardware connection, bolts

possibly seized

Manufactured: 2009

Installed: 2009

Removed: 2018


Material: parking stands are

carbon steel; is the hardware

silicon bronze, zinc plated, 316, or

304

Suggestion: Use 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


Material: parking stands are

carbon steel; is the hardware

silicon bronze, zinc plated, 316, or

304

Suggestion: Use 304

stainless washers and bolts

with 400 series nuts

instead of zinc plated steel

or silicon bronze on carbon

steel


Issue: Rusted ground flange

assembly with bronze padlock,

handle, lever, and shaft

Manufactured: 2006

Installed: 2006

Removed: 2018


Material: grounding welded

assembly is carbon steel; padlock,

lever, and shaft are bronze


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

No corrosion at tank grounding pad.

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

Material: 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


Issue: galvanic corrosion where

dissimilar metals touching silicon

bronze or brass thermal well screw

into welded steel pipe flange

Manufactured: 2005; 3mils of zinc-

rich primer with 3mils of black

epoxy finish top coat

Installed: Boston, Massachusetts

Northeast

Removed: 2017


Material: 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





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 zinc-

rich primer with 3mils of black

epoxy finish top coat

Installed: New England Northeast

Removed: 2017


Material: tank material copper

bearing steel


Issue: None: No rust around

stainless bolt and washer in carbon

steel cover weld nut

Manufactured: 2013

Application: Not Coastal

Material: 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


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

Material: 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 1989.

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.

Material: 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.

Submersible Transformer Galvanic Application Compatibility Chart (STGACC)

Tank

Material

Misc. External

Hardware (e.g.

Bolts, nuts,

washers)

Material

Valves and

Gauges

Material

Screw on

Fittings

Material

Plugs and Caps

Material

Bushing Flanges

Material

Parking

Stands

Material

Copper

Bearing

Steel (Low

Alloy Steel)

Silicon Bronze

(.35V) Tank will

corrode Not-

Recommended

304 (.55V) &

316 (.58V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (.13V)

Stainless Active

(stagnant

water)

Recommended

Silicon Bronze

(.35V) Tank will

corrode Not-

Recommended

304 (.55V) &

316 (.58V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (.13V)

Stainless Active

(stagnant

water)

Recommended

Silicon Bronze

(.35V) Tank will

corrode Not-

Recommended

304 (.55V) &

316 (.58V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (.13V)

Stainless Active

(stagnant

water)

Recommended

Silicon Bronze

(.35V) Tank will

corrode Not-

Recommended

304 (.55V) &

316 (.58V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (.13V)

Stainless Active

(stagnant

water)

Recommended

316 (.23V) Stainless

Active (stagnant

water) Tank will

corrode Not-

Recommended

304 (.55V) & 316

(.58V) Stainless

Non-Active Tank

will corrode Not

Recommended

304 (.13V)

Stainless Active

(stagnant water)

Recommended

Same as

Tank

Material

304

Non-Active

(Passive)

Silicon Bronze

(.2V) External

Hardware will

corrode Maybe

Threshold Not-

Recommended

430 Stainless

(.42V) Active

(stagnant water)

External

Hardware will

corrode Not-

Recommended

430 (.17V)

Stainless

Non-Active

Recommended

Silicon Bronze

(.2V) Valves and

Gauges will

corrode Maybe

Threshold Not-

Recommended

430 Stainless

(.42V) Active

(stagnant water)

Valves and

Gauges will

corrode Not-

Recommended

430 (.17V)

Stainless

Non-Active

Recommended

Silicon Bronze

(.2V) Screw on

Fittings will

corrode Maybe

Threshold Not-

Recommended

430 Stainless

(.42V) Active

(stagnant water)

Screw on

Fittings will

corrode Not-

Recommended

430 (.17V)

Stainless

Non-Active

Recommended

Silicon Bronze

(.2V) Plug and

Caps will

corrode Maybe

Threshold Not-

Recommended

430 Stainless

(.42V) Active

(stagnant water)

Plug and Caps

will corrode

Not-

Recommended

430 (.17V)

Stainless

Non-Active

Recommended


Active (stagnant

water) Flange will

corrode Not-

Recommended

304 (OV) Stainless

same as tank

material

Non-Active

Recommended

316 Stainless

(.03V) Non-Active

Recommended

Same as

Tank

Material

304

Active

(stagnant

water)

Silicon Bronze

(.22V) Tank will

corrode Not-

Recommended

430 Stainless

(.25V) Non-

Active

Tank will

corrode Not-

Recommended

430 (0V)

Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.22V) Tank will

corrode Not-

Recommended

430 Stainless

(.25V) Non-

Active

Tank will

corrode Not-

Recommended

430 (0V)

Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.22V) Tank will

corrode Not-

Recommended

430 Stainless

(.25V) Non-

Active

Tank will

corrode Not-

Recommended

430 (0V)

Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.22V) Tank will

corrode Not-

Recommended

430 Stainless

(.25V) Non-

Active

Tank will

corrode Not-

Recommended

430 (0V)

Stainless

Active (stagnant

water)

Recommended


Non-Active Tank

will corrode Not-

Recommended

304 (OV) Stainless

same as tank

material

Active

(stagnant water)

Recommended

316 Stainless (.1V)

Active (stagnant

water)

Recommended

Same as

Tank

Material

316

Non-Active

(Passive)

Silicon Bronze

(.23V) External

Hardware will

corrode Not-

Recommended

430 Stainless

(.45V) Active

(stagnant water)

External

Hardware will

corrode Not-

Recommended

430 (.2V)

Stainless

Non-Active

External

Hardware will

corrode Maybe

Threshold Not-

Recommended

Silicon Bronze

(.23V) Valves

and Gauges will

corrode Not-

Recommended

430 Stainless

(.45V) Active

(stagnant water)

Valves and

Gauges will

corrode Not-

Recommended

430 (.2V)

Stainless

Non-Active

Valves and

Gauges will

corrode Maybe

Threshold Not-

Recommended

Silicon Bronze

(.23V) Screw on

Fittings will

corrode Not-

Recommended

430 Stainless

(.45V) Active

(stagnant water)

Screw on

Fittings will

corrode Not-

Recommended

430 (.2V)

Stainless

Non-Active

Screw on

Fittings will

corrode Maybe

Threshold Not-

Recommended

Silicon Bronze

(.23V) Plug and

Caps will

corrode Not-

Recommended

430 Stainless

(.45V) Active

(stagnant water)

Plug and Caps

will corrode

Not-

Recommended

430 (.2V)

Stainless

Non-Active

Plug and Caps

will corrode

Maybe

Threshold Not-

Recommended


Active (stagnant

water) Flange will

corrode Not-

Recommended

316 (OV) Stainless

same as tank

material

Non-Active

Recommended

304 Stainless

(.03V) Non-Active

Recommended

Same as

Tank

Material

316

Active

(stagnant

water)

Silicon Bronze

(.12V)

Recommended

430 Stainless

(.15V) Non-

Active

Recommended

430 (.1V)

Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.12V)

Recommended

430 Stainless

(.15V) Non-

Active

Recommended

430 (.1V)

Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.12V)

Recommended

430 Stainless

(.15V) Non-

Active

Recommended

430 (.1V)

Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.12V)

Recommended

430 Stainless

(.15V) Non-

Active

Recommended

430 (.1V)

Stainless

Active (stagnant

water)

Recommended


Non-Active Tank

will corrode Not-

Recommended

316 (OV) Stainless

same as tank

material

Active

(stagnant water)

Recommended

304 Stainless (.1V)

Active (stagnant

water)

Recommended

Same as

Tank

Material

409 Non-

Active

(Passive)

Silicon Bronze

(.02V)

Recommended

304 (.22V) &

316 (.25V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (.2V) & 316

(.1V) Stainless

Active (stagnant

water) External

Hardware will

corrode Maybe

Threshold Not

Recommended

Silicon Bronze

(.02V)

Recommended

304 (.22V) &

316 (.25V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (.2V) & 316

(.1V) Stainless

Active (stagnant

water) Valves

and Gauges will

corrode Maybe

Threshold Not

Recommended

Silicon Bronze

(.02V)

Recommended

304 (.22V) &

316 (.25V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (.2V) & 316

(.1V) Stainless

Active (stagnant

water) Screw on

Fittings will

corrode Maybe

Threshold Not

Recommended

Silicon Bronze

(.02V)

Recommended

304 (.22V) &

316 (.25V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (.2V) & 316

(.1V) Stainless

Active (stagnant

water) Plug and

Caps will

corrode Maybe

Threshold Not

Recommended

409 (OV) Stainless

same as tank

material Non-

Active

Recommended

304 (.2V) & 316

(.1V) Stainless

Active (stagnant

water) Flange will

corrode Maybe

Threshold Not

Recommended

Same as

Tank

Material

409 Active

(stagnant

water)

Silicon Bronze

(.22V) Tank will

corrode Not

Recommended

304 (.42V) &

316 (.45V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (0V) & 316

(.1V) Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.22V) Tank will

corrode Not

Recommended

304 (.42V) &

316 (.45V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (0V) & 316

(.1V) Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.22V) Tank will

corrode Not

Recommended

304 (.42V) &

316 (.45V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (0V) & 316

(.1V) Stainless

Active (stagnant

water)

Recommended

Silicon Bronze

(.22V) Tank will

corrode Not

Recommended

304 (.42V) &

316 (.45V)

Stainless Non-

Active Tank will

corrode Not

Recommended

304 (0V) & 316

(.1V) Stainless

Active (stagnant

water)

Recommended

409 (OV) Stainless

same as tank

material Active

(stagnant water)

Recommended

304 (0V) & 316

(.1V) Stainless

Active (stagnant

water)

Recommended

Same as

Tank

Material

Copper Bearing Steel (Low Alloy Steel) ~ -.63

Silicon Bronze ~ -.28

409 Non-Active ~ -.30




409 Active ~ -.5

430 Active ~ -.5

304 Active ~ -.5

316 Active ~ -.4

Reference:

http://www.ssina.com/corrosion/galvanic.html

http://www.designbyinitiative.com/files/8514/2711/8760/Galvanic_Table.pdf

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.

c57.12.24 galvanic corrosion task force fall 2018 rev 09...

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