Not much sole!

[soldthehouse]

The bacteria referred to by the OP appear to actually remove metals from ores. The mechanism you are describing is more credible, but would refer to a different organism

 

Richard

Ah when I wikied it with the other link in the thread I thought the process involved a chemical reaction and oxygen was mentioned, but I can be innaccurate at times

[MoominPapa]

Thiobacillus ferrooxidans

 

The name implies that these things need suplhur (and probably excrete sulphuric acid). Is your bit of the cut particularly polluted with sulphur compounds, maybe? Do you get the smell of rotten eggs sometimes (hydrogen sulphide)?

 

MP.

Edited August 6, 2010 by MoominPapa

[WotEver]

... credance. (did I spell that wright?)

Not even correct for a bit of Clearwater Revival, which would be useful in this thread

 

Tony

[JohnO]

Interseting to hear you say the anodes are intact. seems to add a bit of credance. (did I spell that wright?)

 

I guess new Anodes when blacked March 2008, it could be 2009, I really struggle with dates. Old Anodes since maybe 2000. Parasal these dates are guesswork, you have the receipts so that should tell you how long the Anodes have been fitted. I think what I am trying to say is, as good as no Anodes for maybe 10 years maybe more. New Anodes not that long.

 

edit to try and make more sense.

and failed.

Edited August 6, 2010 by JohnO

[WotEver]

Thiobacillus ferrooxidans

 

The name implies that these things need suplhur (and probably excrete sulphuric acid). Is your bit of the cut particularly polluted with sulphur compounds, maybe? Do you get the smell of rotten eggs sometimes (hydrogen sulphide)?

 

MP.

According to my Googling it loves sulphur and does indeed excrete H2SO4. It obtains its energy through the oxidation of ferrous iron or reduced inorganic sulphur compounds.

 

However, every reference to it that I can find refers to it thriving in mine workings. A smattering of mentions of it in a marine environment, but not a single mention of it in fresh water.

 

Which is not to say it doesn't live in fresh water, just that it's the first I've ever heard of it (and some other posters too, by the looks of it).

 

Tony

[soldthehouse]

Not even correct for a bit of Clearwater Revival, which would be useful in this thread

 

Tony

My mother went into a music shop in an effort to acquire my brother said album and asked for Creedance clearwater survival, strange what you remember :Dcoincidence that there is a track called green river on it

Edited August 6, 2010 by soldthehouse

[smileypete]

I think the point is that their presence increases the oxygen level thus increasing corrosion, at least thats what ive assumed

No, they love anerobic conditions so would typically live under nodules of rust (covered pits).

 

Maybe loose paint or blacking gives them a start.

 

I think the H2SO4 they create causes accelerated localised galvanic corrosion inside the pit, like a little battery

 

cheers,

Pete.

Edited August 6, 2010 by smileypete

[soldthehouse]

No, they love anerobic conditions so would typically live under nodules of rust (covered pits).

 

Maybe loose paint or blacking gives them a start.

 

I think the H2SO4 they create causes accelerated localised galvanic corrosion inside the pit, like a little battery

 

cheers,

Pete.

Some people can teach, some cant, Thanks for the succint explanation. youve cleared the fog that was in my head

[tillergirl]

sounds like the same buggers that ate the floor of my mini - that always being wet when it rained!

[5thHorseman]

Although there is no need to justify myself, this surveyor came highly recommended and has been involved in the business for many years, written books, lectured and trained many other well respected surveyors. I am not a complete numpty who would drag someone from the street to give me a very important survey on my hull- a hull that has been severly attacked by something that leaves the anodes intact.

 

I was in no way suggesting that you were a numpty or the surveyor was one either.

The problem is that the explanation is one that I have never heard of before and perhaps that goes for many more on this forum.

It is so novel (to me) that we all could suffer the same form of corrosion at any time and appear defenceless against it.

Why are these blighters attacking your boat and doing it severe damage in a short period of time and not doing it to everyone else?

 

If there is an alternative explanation we should all help in establishing what that is.

 

for example

 

Are you sure the anodes are magnesium?

Aluminium and zinc anodes in fresh water can become covered with an oxide coat which seals the anode, stops them working and preserves them.

 

Are you in a marina?

Do you moor against piling?

Is there a anything unusual or special in the water conditions at or near to where you moor the boat?

Are other people locally experiencing accelerated hull thinning?

 

5th

[alan_fincher]

A shame this thread went temporarily of track, as I'm sure there are a lot of people out there would like to understand it better.

 

I personally have never heard of this, (which perhaps means nowt!), but unless there are some very local conditions in the water where this boat is moored, it is hard to understand how something so dramatic has apparently happened so quickly.

 

If we have not driven Parasal away, I would be very keen to learn not just the surveyors view of what it is, but also why it has happened, and why her boat in particular has apparently come under such attack.

 

Surely just treating it, and putting the boat back in the water is not enough to stop it continuing, if (for example) it was actually something in the water causing it ?

[Timleech]

A shame this thread went temporarily of track, as I'm sure there are a lot of people out there would like to understand it better.

 

I personally have never heard of this, (which perhaps means nowt!), but unless there are some very local conditions in the water where this boat is moored, it is hard to understand how something so dramatic has apparently happened so quickly.

 

If we have not driven Parasal away, I would be very keen to learn not just the surveyors view of what it is, but also why it has happened, and why her boat in particular has apparently come under such attack.

 

Surely just treating it, and putting the boat back in the water is not enough to stop it continuing, if (for example) it was actually something in the water causing it ?

 

Maybe it (the bug) is a scientific explanation for the brown blisters which are in fact extremely common on steel canal boats, which when washed off expose pitting to varying degrees. If so, it is a bit surprising to me that no reference to it as a corroding agent seems to come up with simple internet searching.

 

Tim

[Guest User]

No, they love anerobic conditions so would typically live under nodules of rust (covered pits).

 

Maybe loose paint or blacking gives them a start.

 

I think the H2SO4 they create causes accelerated localised galvanic corrosion inside the pit, like a little battery

 

cheers,

Pete.

Some people can teach, some cant, Thanks for the succint explanation. youve cleared the fog that was in my head

 

Sorry, but Thiobacillus is a genus of aerobic bacteria, but there are other micro-organisms, both aerobic and anaerobic, that can also cause metal corrosion.

 

For those that are interested, maybe here is a good place to start CLICKY, or google "microbial corrosion" ? but hey, what do I know.

[soldthehouse]

Sorry, but Thiobacillus is a genus of aerobic bacteria, but there are other micro-organisms, both aerobic and anaerobic, that can also cause metal corrosion.

 

For those that are interested, maybe here is a good place to start CLICKY, or google "microbial corrosion" ? but hey, what do I know.

Just when I thought it was safe to go back in the water

[smileypete]

Sorry, but Thiobacillus is a genus of aerobic bacteria, but there are other micro-organisms, both aerobic and anaerobic, that can also cause metal corrosion.

 

For those that are interested, maybe here is a good place to start CLICKY, or google "microbial corrosion" ? but hey, what do I know.

My bad, I just assumed it was anerobic sulphur reducing bacteria (SRB).

 

If the corrosion comprised shiny pits covered with rust (I've seen this a couple of times myself ), it seems likely to be that:

 

'For example, within active corrosion pits, the oxygen content becomes exceedingly low.' (clicky)

 

Maybe the basin the boat was moored in for a while was used for handling coal some years ago, possibly a bit stagnant too.

 

cheers,

Pete.

[DandV]

I have had experience of pit corrosion both internal and external on buried steel underground fuel storage tanks. These corrosion failures led to a rapid industry replacement of steel systems with plastic secondary contained systems here in New Zealand

Internal corrosion was rare, but never the less devastating, and was characterised by few, sometimes only just one, deep parallel sided pits with a white shiny active surface. If it did occur it was at the tank low point of a diesel or paraffin tank. It was attributed to the presence of a particular type of diesel bug, presumably thiobacillus ferric oxide.living in water below the fuel and producing local sulphuric acid in the pit. Some failures were in tanks under five years old

Failure from external corrosion was much more common.

There were generally two forms. The most severe was an attack by anaerobic bacteria resulting in generally crater pits covered in black slime that could be wiped off with your finger revealing bright white metal that that in just a few minutes would dull and develop a rust red film. Some tanks lost kilograms of steel a year. Another characteristic of this attack was the rotten egg smell of hydrogen sulphate. This type of corrosion was particularly present in tanks installed in estuarine and peaty locations.

The other type of external corrosion was electrolytic corrosion causing a number of pits often with near parallel sides. Sometimes the pits would accurately show where lifting chains had been used in carting the tanks to site prior to installation. The electrical source could be mains earthing or dissimilar metals, even very slightly dissimilar metals like the adjacent plates. Where a new tank was installed in an existing system and electrically connected via pipework to existing tanks it was the new tank that was prone to premature failure

 

To mitigate external failures the initial response was to improve tank coatings, but by it self it proved counterproductive as it concentrated the metal removal by at the inevitable breaks in the coating. When however combined with cathodic protection using either impressed or sacrificial systems and electrical isolations it was useful in reducing failure rates until the total storage system replacement program was completed.

 

What is the relevance with canal boats?

Hulls will be prone to electrolytic corrosion which can be greatly exacerbated by faulty electrical systems both 230VAC and the DC systems. Well designed and maintained electrical systems, good anodes and good coatings provide effective mitigation.

 

I would suspect that that any portion of the hull sitting directly on mud canal bottoms would provide suitable conditions for anaerobic corrosion.

 

And yes there are steel devouring bugs.

 

Cheers Don

[WotEver]

For those that are interested, maybe here is a good place to start CLICKY, or google "microbial corrosion" ?

Scary stuff - particularly the last image on that page:

 

Tony

Edited August 9, 2010 by WotEver

[RLWP]

I have had experience of pit corrosion both internal and external on buried steel underground fuel storage tanks. These corrosion failures led to a rapid industry replacement of steel systems with plastic secondary contained systems here in New Zealand

Internal corrosion was rare, but never the less devastating, and was characterised by few, sometimes only just one, deep parallel sided pits with a white shiny active surface. If it did occur it was at the tank low point of a diesel or paraffin tank. It was attributed to the presence of a particular type of diesel bug, presumably thiobacillus ferric oxide.living in water below the fuel and producing local sulphuric acid in the pit. Some failures were in tanks under five years old

Failure from external corrosion was much more common.

There were generally two forms. The most severe was an attack by anaerobic bacteria resulting in generally crater pits covered in black slime that could be wiped off with your finger revealing bright white metal that that in just a few minutes would dull and develop a rust red film. Some tanks lost kilograms of steel a year. Another characteristic of this attack was the rotten egg smell of hydrogen sulphate. This type of corrosion was particularly present in tanks installed in estuarine and peaty locations.

The other type of external corrosion was electrolytic corrosion causing a number of pits often with near parallel sides. Sometimes the pits would accurately show where lifting chains had been used in carting the tanks to site prior to installation. The electrical source could be mains earthing or dissimilar metals, even very slightly dissimilar metals like the adjacent plates. Where a new tank was installed in an existing system and electrically connected via pipework to existing tanks it was the new tank that was prone to premature failure

 

To mitigate external failures the initial response was to improve tank coatings, but by it self it proved counterproductive as it concentrated the metal removal by at the inevitable breaks in the coating. When however combined with cathodic protection using either impressed or sacrificial systems and electrical isolations it was useful in reducing failure rates until the total storage system replacement program was completed.

 

What is the relevance with canal boats?

Hulls will be prone to electrolytic corrosion which can be greatly exacerbated by faulty electrical systems both 230VAC and the DC systems. Well designed and maintained electrical systems, good anodes and good coatings provide effective mitigation.

 

I would suspect that that any portion of the hull sitting directly on mud canal bottoms would provide suitable conditions for anaerobic corrosion.

 

And yes there are steel devouring bugs.

 

Cheers Don

 

Hi Don,

 

thanks for this, it's a really useful post. The "crater pits covered in black slime that could be wiped off with your finger revealing bright white metal" is what Tawny Owl had the first time we had her surveyed. She's now in different waters and living a different life too, and this hasn't reoccurred.

 

Metal munching bugs!

 

Richard

[parasal]

Is it safe to come back in??

Some varied and interesting responses and to answer all at once.......

The shape of the pitting denotes it's cause-shallow pits with bright white/silver at their base as opposed to deep conical pitting caused by electolisis

A hull that was not in the best conditioning the first place

A deep hull that often sits in the sludge at the bottom of the canal

Often mooring near farm land where various nitrates etc can be washed into water

 

And to note that the "bugs" have not caused all the damage- they exist on an old and already detiorating hull

 

If someone can recommend a way to post or have access to an attachment you could read paper written by the surveyor on the subject and included in his manual to marine survey

 

Anyway- all cleaned and blacked and off back to canal to save up for a year- thanks for most of your help and advise!

[luctor et emergo]

Is it safe to come back in??

Some varied and interesting responses and to answer all at once.......

The shape of the pitting denotes it's cause-shallow pits with bright white/silver at their base as opposed to deep conical pitting caused by electolisis

A hull that was not in the best conditioning the first place

A deep hull that often sits in the sludge at the bottom of the canal

Often mooring near farm land where various nitrates etc can be washed into water

 

And to note that the "bugs" have not caused all the damage- they exist on an old and already detiorating hull

 

If someone can recommend a way to post or have access to an attachment you could read paper written by the surveyor on the subject and included in his manual to marine survey

 

Anyway- all cleaned and blacked and off back to canal to save up for a year- thanks for most of your help and advise!

 

 

Glad it's all working out, and as for the responses... that is just the way the forum works. Inbetween the useless, the insulting, and the hilarious replies, there will always be the sensible and usefull replies. You just have to go with the flow...

 

:lol:

[RLWP]

I'm also glad to hear you are back on the water. As I said earlier we rode that emotional roller-coaster of "it's wrecked/it's scrap/it's too expensive/it's Ok!" a couple of years ago. It sounds like your solution was even cheaper than ours in the end.

 

Happy boating

 

Richard

[Proper Job]

.....................A deep hull that often sits in the sludge at the bottom of the canal....................

That'll be mine then

 

I've always thought of mine being the most polished base plate as it ploughs its way along

 

At least a 15mm original thickness gives me a fighting chance.

[parasal]

Glad it's all working out, and as for the responses... that is just the way the forum works. Inbetween the useless, the insulting, and the hilarious replies, there will always be the sensible and usefull replies. You just have to go with the flow...

 

:lol:

I know and normally I would join in but all this stress tends to create a bypass in the sense of humour node! Sorry for any stropiness!

Still, good insurance news- they reckon they'll pay for the rudder(the reason I came outing the first place!) and it comes off last years claim year so still have fully intact no claims! Feel a bit guilty for dropping the other boat in it but that's another story!

Cheers all xx