Green Corrosion on Bronze Fittings

[Traveler 45C]

Correct me if I’m wrong. Galvanic corrosion causes the bronze to de-zincify, causing the metal to take on a pinkish color and weakening it. Bonding protects the metal by connecting all underwater metals together, placing them all at the same electrical potential, thereby elimination any current flow between them.

So what’s causing the green corrosion in the attached pic?

Is it a result of poor bonding also?

Does this type corrosion cause a weakening of the metal?

Or is it just normal oxidation that can be reduced simply by coating the metal with WD-40 or some other corrosion blocker?

Related question:

In my A/C system, the pump is bonded. The water outlet is nylon with a rubber hose attached that goes to a bronze fitting. Does this bronze fitting need to be bonded also? It has no connections to any other metal. The only path current could take is through the water flowing through it.

 

[Boatsb]

Green is oxidation. Pink is galvanic.

 

[Will]

I'd give that stuffing box a good inspection at your next haulout. Wire brush and tap the bronze bolts, nuts and fittings with a hammer. Replace the hose clamps etc. I've found weakened, yellowish bronze (not brass and not the golden color of solid bronze) under that kind of corrosion in the past. Chit-chat with some good salt water boat yard guys about it.
Will

 

[Traveler 45C]

This stuffing box isn't mine, just used it to show the green corrosion. My questions in the first post are to address the causes of it.

 

[Brian Degulis]

Exposure to sea water is going to turn it green. If you see it on a strainer there is a leak or seep but on a paking gland unless it's greasy or oily it's going to turn green.

Brian

 

[Traveler 45C]

So, will the oxidation weaken the metal?

 

[MikeP]

No. Spray it with corrosion x and it (or most of it anyway) will disappear with a wipe. Spray it periodically and it will prevent it from appearing in the first place.

 

[REBrueckner]

Post #8 also reflects my experience...

I've come to believe, without proof or firm evidence, that green corrosion is the simple oxidation of bronze alloys (from exposure to oxygen and salt water) while the white is at least in part salt that most likely results when a small insignificant salt water ooze evaporates and leaves the salt content behind....in perhaps a 100 or 150 years that part might need a close inspection....stainless steel hose clamps don't fair as well being MORE active than silicon bronze and subject to crevice corrosion and poor quality screws...so they deserve to be replaced....coating a new hose clamp on a shaft log with a corrosion preventative or water pump type grease helps avoid premature failure....and do the studs and nuts at the same time so when you need to snug up the stuffing box its easy....

I seem to remember tasting the white stuff MANY years ago and I think it might have been salty (as expected) but bitter(unexpected)...

In anyone from the great lakes also has the white deposit on their shaft log and the boat has always been fresh water, that would shoot down my brilliant theory...

 

[Brian Degulis]

So, will the oxidation weaken the metal?

No at least not in a practical sense. Unlike steel bronze and copper and some aluminum oxidize on the surface and stop in a sense they protect themselves. The Statue Of Liberty is bare copper sitting out in the elements it goes green and that's it. You need another factor to harm it like electrolysis. I think trapped moisture can harm it also I've seen copper pipe go bad under the copper straps that hold it in place. But copper pipe is very thin packing glands are thick castings. I learned just recently that the Buck Algonquin packing glands that most of us have are not bronze they're red brass. I ordered a bunch and when the engineering drawings arrived they were specing red brass for the foundry. I called them and learned that all they're harware is actually red brass and simply referred to as bronze.

Brian

 

[Traveler 45C]

Ok, thanks guys.

Now, on to my other question:

In my A/C system, the pump is bonded. The water outlet is nylon with a rubber hose attached that goes to a bronze fitting. Does this bronze fitting need to be bonded also? It has no connections to any other metal. The only path current could take is through the water flowing through it.

 

[Brian Degulis]

Yes



Brian

 

[REBrueckner]

no.....but it's a long complicated and boring discussion, ultimately without a final resolution......and has been dissected on the forum previously....

silicon bronze with sit happily in salt water for an almost unlimited period of time without problems,,,but when you get different metals or stray currents corrosion problems can occur....one reason to like synthetic hoses and plastic/synthetic fittings unless strength is required.....

 

[Brian Degulis]

I know some don't believe in bonding underwater fittings and I guess that's what your refering to. His boat I'm assuming is bonded so in his case you wouldn't want one fitting isolated and the rest bonded would you?



Brian

 

[bostonhatteras]

interesting to hear about the "red brass" being spec'ed for the Buck Algonquin underwater metal products. these are not inferior products at all, as most propellors and other items we call bronze are really a brass. bronze being an alloy of copper and another metal such as silicon or aluminum or nickel and brass being an alloy of copper and zinc of varying proportions. strangely enough the strongest brass is 60/40 brass/zinc. the color of your bright and shiny reconditioned propellors is yellow just like a symbal on a drum set. the yellow color is from the zinc. bronzes have a reddish color. it doesnt matter what the outside 'as cast' color is, file a bit away to see shiny metal inside and that will give you a good indication if its brass or bronze. just keep the sacrificial zincs up and no problems will arise.

 

[krush]

I know the original question was already answered, but here is my answer: What color is the Statue of Liberty?

 

[yachtsmanbill]

I know the original question was already answered, but here is my answer: What color is the Statue of Liberty?

What color is the frame?? ws

 

[REBrueckner]

Unless you are forced to use red brass, don't. If Buck IS using red brass they ARE now inferior.

I'm not sure just what post #15 says but here is the correct composition as I have posted many prior times:
traditional Props, rudders, and bolts: managanese bronze and subject to possible corrosion on ss shafts; hence shaft zincs and rudder zincs a necessity on SS shafts like aquamet 22 for recreational boats.

I think NIBRAL props are nickel and brass, another high quality bronze alloy...I am unsure of their galvanic activity....so zincs recommended....

Seacocks and highest quality fasteners: silicon bronze, will sit almost forever with or without zincs....

There should be little measureable ZINC in quality props...ZINC in brass is what causes it to corrode

Here is one list, most active first, least active last: Tin, managanese bronze, naval brass,yellow brass,admiralty brass, copper,brass,silicone bronze, lead.

There are many other alloys and the quality and uniformity and impurities of the alloy is just as important as the ingredients and name.

 

[REBrueckner]

"I know some don't believe in bonding underwater fittings and I guess that's what your refering to. His boat I'm assuming is bonded so in his case you wouldn't want one fitting isolated and the rest bonded would you?"

That's the issue....isolating a quality alloy is actually just fine....but not everyone agrees. I have several previous posts on this issue. No huge deal either way if the metal is a quality marine alloy. When I was an ABYC member there were so many "old school" advisors/experts that new ideas were impossible to adopt....I no longer know the politics.....

If things are bonded you actually INCREASE the risk of underwater metal deterioriation (electrolytic corrosion and galvanic corrosion) via electrical leakage and or induced voltages present in water...but with good zincs nearby you ARE usually protected until the zincs are gone. An isolated piece of quality metal is actually least active in most configurations.

The practical issue is that zincs are usually NOT close enough to offer protection in association with bonding and so electrical leakages will ruin otherise isolated fittings. Shaft zincs, for example, should be close to props as shaft zincs protect manganese bronze props not Aquamet 22 shafts...Older all bronze underwater traditional boats likely need no bonding especially older wood boats...

On my prior wood Matthews, I studied this extensively (because I had some softening of wood around a few seacocks) and even wrote an article for the Matthews Boat Owners Association..."if you have soft wood around bronze seacocks or shaft logs, disconnect the bonding wire to prevent galvanic currents (from zinc) eating up the lignin in your planks (lignin is the wood cell stiffener).....and limit the amount of zinc you use..."

All this is unimportant on fiberglass hulls...fiberglass seems pretty impervious to such small protection currents...wood is NOT.

Keep in mind this is a bonding NOT a grounding discussion.....

For those who care, Spa Creeks THE 12VOLT DOCTORS HANDBOOK is a classic reference and discusses all this in easy to understand language...and intricate detail.

Another reference is Yacht Corrosion Consultant's BOAT AND YACHT CORROSION CONTROL. They make the Corrosion Test Meter which I and a few here own and have recommended.

 

[Paul45c]

Greg, back to your original question on the corrosion on that stuffing box, it looks like it's just weeping from the hose. If it were me I'd replace that hose with a blue silicon one at the next haulout and the owner would never have to worry about it again.

Someone suggested Corrosion X on it, which is a great idea. Prior to that, though, take some phosphoric acid and some small wire brushes to clean it up nicely to it's original color and get the scale off it. The Corrosion X will keep it nice with just a few touchups every so often.

 

[Brian Degulis]

Unless you are forced to use red brass, don't. If Buck IS using red brass they ARE now inferior.

I'm not sure just what post #15 says but here is the correct composition as I have posted many prior times:
traditional Props, rudders, and bolts: managanese bronze and subject to possible corrosion on ss shafts; hence shaft zincs and rudder zincs a necessity on SS shafts like aquamet 22 for recreational boats.

I think NIBRAL props are nickel and brass, another high quality bronze alloy...I am unsure of their galvanic activity....so zincs recommended....

Seacocks and highest quality fasteners: silicon bronze, will sit almost forever with or without zincs....

There should be little measureable ZINC in quality props...ZINC in brass is what causes it to corrode

Here is one list, most active first, least active last: Tin, managanese bronze, naval brass,yellow brass,admiralty brass, copper,brass,silicone bronze, lead.

There are many other alloys and the quality and uniformity and impurities of the alloy is just as important as the ingredients and name.

Acording to Buck They have always used red brass on all they're fittings. They also said that the fittings you buy as bronze are in fact red brass it's just a terminolgy thing. It surprised me and of course there is always a posibility that I'm getting bad info. But it is speced in they're engineering drawings and I did speak with the head of they're engineering dept.

Brian