SteveA
Well-Known Member
Can anyone tell me what is causing the stainless on our 1 year old boat to go brown - it's even streaking down the GRP. What I can do to stop it!
Stainless Steel
- Thread starter SteveA
- Start date
yobbo
Member
Stainless can go brown slitghtly but not to the extent it streaks down your Boat. Get a magnet and put it on your stainless if it sticks its poor quaility it should not stick to 316 or 304. Stainless Steel also retains its rust free look because the outer surface oxidises so if you continually clean it, it will go brownish especially if you use proprietry brand cleaners. Best thing to clean stainless is a scotchbrite apd as well better then all the fancy cleaning products. If your boats only a year old I be talking to the builder as well to see if he can explain it
G
Guest
Guest
Is it the stainless surface or is it from the joint with the GRP hull?
If it is the surface then it is very poor stainless, or you need to clean it thoroughly as some one ground/polished with mild steel contaminated equipment.
If it is a bracket or chainplate and the surface is clean but a brown stain is all around the edge then the fitting was put on without Sikaflex. The gap fills with water/moisture and due to the distance and thinness there is not enough air to keep the stainless from corroding. In this case it would have to be removed and resealed.
Choices are:
1. Dry and cleaned of salt
2. Wet/moist and plenty of air
3. Underwater and an anode.
If it is the surface then it is very poor stainless, or you need to clean it thoroughly as some one ground/polished with mild steel contaminated equipment.
If it is a bracket or chainplate and the surface is clean but a brown stain is all around the edge then the fitting was put on without Sikaflex. The gap fills with water/moisture and due to the distance and thinness there is not enough air to keep the stainless from corroding. In this case it would have to be removed and resealed.
Choices are:
1. Dry and cleaned of salt
2. Wet/moist and plenty of air
3. Underwater and an anode.
CPD
Well-Known Member
Interesting question this. I am about to replace the shroud chainplates on my 30 year old centaur due to rust stains on the GRP in the vicinity of the plates. I have learned that this is almost certainly crevice corossion caused by, as others have said, poor sealing. The corossion can eat away at the through deck fitting resulting in sudden rigging failure.
The question I would want to be answered in your case is, if you simply clean up and re-seal the joint, will that stop any corrosion that has already taken place, or should you have the plates rebedded and re-sealed at the same time ?. I can only imagine that after a year, it would be the former, but I would want to ask a rigging company, just in case. Good luck with it !
The question I would want to be answered in your case is, if you simply clean up and re-seal the joint, will that stop any corrosion that has already taken place, or should you have the plates rebedded and re-sealed at the same time ?. I can only imagine that after a year, it would be the former, but I would want to ask a rigging company, just in case. Good luck with it !
VicS
Well-Known Member
Mostly answered already but to add a little and confirm what has already been said:
If the staining is coming from behind then the fittings need re-bedding paying particular attention to sealing the fastenings otherwise crevice corrosion will eat them away slowly.
If the staining is originating from regions around welds then it is probably due to the metallurgy of the fitting having been affected by the heat from the weld. A little is not unusual but it should not be as bad as you are experiencing. Cliff will advise if he see the post.
If it is generally all over the fitting then it is probably made from an unsuitable alloy or one that is not up to spec. Do the magnet test as advised.
If the staining is coming from behind then the fittings need re-bedding paying particular attention to sealing the fastenings otherwise crevice corrosion will eat them away slowly.
If the staining is originating from regions around welds then it is probably due to the metallurgy of the fitting having been affected by the heat from the weld. A little is not unusual but it should not be as bad as you are experiencing. Cliff will advise if he see the post.
If it is generally all over the fitting then it is probably made from an unsuitable alloy or one that is not up to spec. Do the magnet test as advised.
misterg
Well-Known Member
[ QUOTE ]
Best thing to clean stainless is a scotchbrite pad (<--was 'apd')
[/ QUOTE ]
I am surprised at this - doesn't it leave the surface scratched & dull? What 'grade' (i.e. colour) of Scotchbrite do you use - I am most familiar with the maroon pads, which are excellent at cleaning up pretty much any metal, but are pretty abrasive.
To the OP: I thought 'stainless' was best at resisting corrosion if it had a polished surface - 'Autosol' polish works very well for me, and is available in pretty much every car accessory shop. If your 'brown' wipes off with this, I wouldn't worry. Once polished, the stainless should resist going brown better, and will probably only need going over once / twice a year to keep it bright.
[edit] To clarify - the above applies if it is the metal itself that's going brown. If it is staining from the joints, then I echo the advice already given: Take off, dry & clean, then re-bed. Don't just seal the moisture in![/edit]
My 0.02p
Andy
Best thing to clean stainless is a scotchbrite pad (<--was 'apd')
[/ QUOTE ]
I am surprised at this - doesn't it leave the surface scratched & dull? What 'grade' (i.e. colour) of Scotchbrite do you use - I am most familiar with the maroon pads, which are excellent at cleaning up pretty much any metal, but are pretty abrasive.
To the OP: I thought 'stainless' was best at resisting corrosion if it had a polished surface - 'Autosol' polish works very well for me, and is available in pretty much every car accessory shop. If your 'brown' wipes off with this, I wouldn't worry. Once polished, the stainless should resist going brown better, and will probably only need going over once / twice a year to keep it bright.
[edit] To clarify - the above applies if it is the metal itself that's going brown. If it is staining from the joints, then I echo the advice already given: Take off, dry & clean, then re-bed. Don't just seal the moisture in![/edit]
My 0.02p
Andy
VicS
Well-Known Member
[ QUOTE ]
What 'grade' (i.e. colour) of Scotchbrite do you use - I am most familiar with the maroon pads, which are excellent at cleaning up pretty much any metal, but are pretty abrasive.
[/ QUOTE ]
I did not know there were diffrent grades, I've only ever seen green ones!
However SWMBO has special pad for stainless steel. A grey layer on a small sponge. Presumably it came from a hardware store or maybe Bettaware or Kleeneze.
What 'grade' (i.e. colour) of Scotchbrite do you use - I am most familiar with the maroon pads, which are excellent at cleaning up pretty much any metal, but are pretty abrasive.
[/ QUOTE ]
I did not know there were diffrent grades, I've only ever seen green ones!
However SWMBO has special pad for stainless steel. A grey layer on a small sponge. Presumably it came from a hardware store or maybe Bettaware or Kleeneze.
maxi
Well-Known Member
This can also be caused by stray electricty and thats what it sounds like to me.
Do you have a radio aerial connected to the rigging or guardrail? or, is there an electrical cable trapped somewhere against a fitting?
Try a multi meter connected between one of the affected fittings and the water - if there is a voltage reading then that's your problem. Measure with the boats electrics on and off.
Do you have a radio aerial connected to the rigging or guardrail? or, is there an electrical cable trapped somewhere against a fitting?
Try a multi meter connected between one of the affected fittings and the water - if there is a voltage reading then that's your problem. Measure with the boats electrics on and off.
seaesta
Well-Known Member
Stainless is only stainless when there is an unbroken oxide layer on the surface. The layer can be broken in a number of ways especially if the surface is contaminated with iron (or iron in steel). This contamination can come from externally (such as grinding or filing residue) or internally. Once the iron is at the surface it acts like a wick conducting more iron to the surface. Once established the way to stop this process is to passivate the surface. This passivation is done be immersing the item in hot nitric or citric acid solution - there are various combinations of temperature, time and concentration to get good results and you may ned to experiment.
The other way stainless tends to corrode is if there is no free oxygen to maintain the oxide layer. So if stainless is away from the air it can easily corrode.
A recognised way of testing stainless for corrosion resistance is a boil test. Immerse the item in boiling distilled water for 20 minutes/ Let the stainless stand in the pan for 3 hours then leave it in ambient air to dry - un-passive stainless will show surface rust quite quickly.
The above explains why stainless building exteriors tend to get scrapped once they show surface rust - there is no way to passivate them. It may be next to impossible to stop your deck gear corroding once it has started. I would be pleased to hear from anyone who has a proven solution to this problem
Martin
The other way stainless tends to corrode is if there is no free oxygen to maintain the oxide layer. So if stainless is away from the air it can easily corrode.
A recognised way of testing stainless for corrosion resistance is a boil test. Immerse the item in boiling distilled water for 20 minutes/ Let the stainless stand in the pan for 3 hours then leave it in ambient air to dry - un-passive stainless will show surface rust quite quickly.
The above explains why stainless building exteriors tend to get scrapped once they show surface rust - there is no way to passivate them. It may be next to impossible to stop your deck gear corroding once it has started. I would be pleased to hear from anyone who has a proven solution to this problem
Martin
misterg
Well-Known Member
[ QUOTE ]
I did not know there were diffrent grades, I've only ever seen green ones!
[/ QUOTE ]
There are loads of grades, which are characterised by their colour. I recall a chart that compared them all, but can't find it.
This site lists some of them (no connection).
The 3M web-site is less than helpfull, this is the most complete list I could find, but I'm not convinced that it's all of them. Everything seems to be grouped by purpose, rather than product line (if you see what I mean).
I think the green 'domestic' ones fit into this scheme, as would the light grey 'polishing' pads referred to above.
Sorrry, partial answer. If I can remember where I saw the complete list I'll post it.
Andy
I did not know there were diffrent grades, I've only ever seen green ones!
[/ QUOTE ]
There are loads of grades, which are characterised by their colour. I recall a chart that compared them all, but can't find it.
This site lists some of them (no connection).
The 3M web-site is less than helpfull, this is the most complete list I could find, but I'm not convinced that it's all of them. Everything seems to be grouped by purpose, rather than product line (if you see what I mean).
I think the green 'domestic' ones fit into this scheme, as would the light grey 'polishing' pads referred to above.
Sorrry, partial answer. If I can remember where I saw the complete list I'll post it.
Andy
SteveA
Well-Known Member
Many thanks for all of the replies. It's nothing to do with IWO joints, the boat is a Bene 21.7 and the S/S in question is just about everything on board; the standing rigging, bottle screws, the outboard bracket, the plate the bracket fastens to, shackles, etc.
The stray current idea is one I hadn't considered but seems the most likely - she's out of the water on a trailer now so if this staining doesn't reappear again until I relaunch I guess that would prove it. If that was tha case how would I stop it (surely I don't need to bond everything together!). If it does reappaers while she's on the trailer I'll be at a loss.
I've just tried a (powerful) magnet on most of the bits and find the they all have at least a slight attraction, these include parts from Plastimo, Harken, Z Spars, Barton, etc. I then tried the magnet on some S/S released from work and there was no attraction at all. Could it just be that the general quaity being used isn't the best?
The stray current idea is one I hadn't considered but seems the most likely - she's out of the water on a trailer now so if this staining doesn't reappear again until I relaunch I guess that would prove it. If that was tha case how would I stop it (surely I don't need to bond everything together!). If it does reappaers while she's on the trailer I'll be at a loss.
I've just tried a (powerful) magnet on most of the bits and find the they all have at least a slight attraction, these include parts from Plastimo, Harken, Z Spars, Barton, etc. I then tried the magnet on some S/S released from work and there was no attraction at all. Could it just be that the general quaity being used isn't the best?
VicS
Well-Known Member
[ QUOTE ]
This passivation is done be immersing the item in hot nitric or citric acid solution
[/ QUOTE ] Not something one would recommend for the home DIYer at least not hot nitric acid.
According to the couple of websites I looked at stainless steel will repassivate itself reasonably quickly simply on exposure to air!
This passivation is done be immersing the item in hot nitric or citric acid solution
[/ QUOTE ] Not something one would recommend for the home DIYer at least not hot nitric acid.
According to the couple of websites I looked at stainless steel will repassivate itself reasonably quickly simply on exposure to air!
rogerthebodger
Well-Known Member
Wichard do a paste called Wichinox that was sold to clean and re-passivate stainless. I have a tube but never used it so cannot say how effective it is.
I tend to mechanical polish all the stainless fittings I make and then keep it free of rust with chemico with non abrasive sponge.
3M green sponge scratches too much, the pink one is said to be OK but again not used in anger.
I tend to mechanical polish all the stainless fittings I make and then keep it free of rust with chemico with non abrasive sponge.
3M green sponge scratches too much, the pink one is said to be OK but again not used in anger.
wotayottie
Well-Known Member
[ QUOTE ]
Could it just be that the general quaity being used isn't the best?
[/ QUOTE ]
You've probably got the answer there - you didnt pay Swedish boat prices and so cant expect Swedish boat quality. Having said that, have a look round your local marina and I bet you can find some brown stains somewhere on almost every boat.
But dont worry - if the rust (which is what it is) is only very light and on open surfaces, it will take an awful long time before it becomes a structural issue. The bit to worry a bit more about is where it seems to be weeping from between a fitting such as a chainplate and the grp its sat on. All common grades of stainless can rust very quickly if there is a lack of oxygen, which might occurr for example where a fitting is poorly bedded on sealant, water gets in and stagnates. As an illustration, I once took some 14mm bolts out of the skegs of my last boat and not one out of 10 was fit for re-use. Several came out in bits. All because the sealant wasnt properly applied. And these bolts were 316 or A4.
Ignore the magnetism bit - any austenitic becomes slighlty more permiable when cold worked. Indeed, you are ever so slightly magnetic!
Could it just be that the general quaity being used isn't the best?
[/ QUOTE ]
You've probably got the answer there - you didnt pay Swedish boat prices and so cant expect Swedish boat quality. Having said that, have a look round your local marina and I bet you can find some brown stains somewhere on almost every boat.
But dont worry - if the rust (which is what it is) is only very light and on open surfaces, it will take an awful long time before it becomes a structural issue. The bit to worry a bit more about is where it seems to be weeping from between a fitting such as a chainplate and the grp its sat on. All common grades of stainless can rust very quickly if there is a lack of oxygen, which might occurr for example where a fitting is poorly bedded on sealant, water gets in and stagnates. As an illustration, I once took some 14mm bolts out of the skegs of my last boat and not one out of 10 was fit for re-use. Several came out in bits. All because the sealant wasnt properly applied. And these bolts were 316 or A4.
Ignore the magnetism bit - any austenitic becomes slighlty more permiable when cold worked. Indeed, you are ever so slightly magnetic!
tyce
Well-Known Member
[ QUOTE ]
I then tried the magnet on some S/S released from work ?
[/ QUOTE ]
ahemmm care to tell me more about this bit of stainless, i wondered where that hp smoc compressor had gone)
apologys for thread drift
I then tried the magnet on some S/S released from work ?
[/ QUOTE ]
ahemmm care to tell me more about this bit of stainless, i wondered where that hp smoc compressor had gone)
apologys for thread drift
yobbo
Member
I use Green scotchbrite pads the garden variety supermarket kind use lightly damp with freshwater the dont scratch Bright Stainless work . The idea to use them came from a bloke at my sons work who makes all their polished bowrails pushpits pullpits etc for the Boats the firm he works for makes
rogerthebodger
Well-Known Member
Interesting
The first pic is the kind of finish I get polishing with normal polishing soap and a power polishing mop on a 2 Kw angle grinder.
and this is what happened when one of my staff atacked a simular item I polished to the same quality as above with a green scotchbrite pad
May be the ones in OZ are not a hard as the ones we get in RSA.
The first pic is the kind of finish I get polishing with normal polishing soap and a power polishing mop on a 2 Kw angle grinder.
and this is what happened when one of my staff atacked a simular item I polished to the same quality as above with a green scotchbrite pad
May be the ones in OZ are not a hard as the ones we get in RSA.
maxi
Well-Known Member
Stray Current
With what you say, it does seem ever more liekely to be the problem. It appears that your rigging has a connection to a power supply and that there is some sort of connection to your guard wires, pulpit etc, possibly through the toe rail?
It will be a tedious task checking voltage measurements on just one circuit at a time - but necessary.
I have found this sort of problem in: a car radio aerial feeding back through a shroud (major rusting), a cabing light cable pinched by chain plate and a cabin light circuit chafing under a stanchion bracket. In each case these provided a circuit between fittings and the sea, particularly in wet weather.
Good luck.
With what you say, it does seem ever more liekely to be the problem. It appears that your rigging has a connection to a power supply and that there is some sort of connection to your guard wires, pulpit etc, possibly through the toe rail?
It will be a tedious task checking voltage measurements on just one circuit at a time - but necessary.
I have found this sort of problem in: a car radio aerial feeding back through a shroud (major rusting), a cabing light cable pinched by chain plate and a cabin light circuit chafing under a stanchion bracket. In each case these provided a circuit between fittings and the sea, particularly in wet weather.
Good luck.
bigmart
Well-Known Member
I had a similar problem with some buiding fittings that were used in an exposed sea front application. After much research I was told the problem wwas caused by Chrome Migration caused by the exceptionally high salt deposits which were deposited by spray then the air drying the spray. The Chrome looks more Orange than rust but its easy to confuse the two.
I was told that Polished Stainless is much more resistant than Satin so I would avoid the Sctchbright at all costs.
Several of the experts I spoke to recommended Jif, or as it is now called Cif as the best restorer of the Stainless surface.
Martin
I was told that Polished Stainless is much more resistant than Satin so I would avoid the Sctchbright at all costs.
Several of the experts I spoke to recommended Jif, or as it is now called Cif as the best restorer of the Stainless surface.
Martin
SteveA
Well-Known Member
I've decided to try the battery concept and put an Anode on the keel to see if this stops the problem - trouble is the boats out now until next year.
To Nosy- at least it's not 750kgs!
Thanks for all of the suggestions
To Nosy- at least it's not 750kgs!
Thanks for all of the suggestions