Silicon Bronze vs Stainless

What kind, options, etc.

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Postby upspirate » Fri Feb 20, 2009 12:30 pm

Brass is not strong enough

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Postby Nova SS » Fri Feb 20, 2009 2:36 pm

Denon Osterman wrote:What about brass?

Are you thinking about the screws that Noahs marine offers? I personally like them. Especially since they have that unique Canadian invention the robertson screw head. IMHO in most of our applications the screws are only there to hold the parts together until the epoxy sets up. (sort of like a clamp) They are what I will be using.

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Postby v8viking » Sun Jun 07, 2009 1:35 pm

basilkies wrote:It's a no brainer, stainless is only good as stainless when it is exposed to the
air. I can't go into the science of it but once it is in an airless environment it loses its stainless property and can rust.

Hello everybody!
If I understand this problem correctly, there seems to be a lot of misunderstanding here.
Stainless steel does not loose it`s properties when covered or encapsulated!
In the yard where I work(Norway) we build the biggest oilrigs in the world with tons and tons of stainless on them, some of it painted, some not.These rigs are built with a life expectancy of 50-70 years!!
And all of this in the harshest most corrosive environments in the world.
They wouldn`t use stainless if this was a problem!!, but on the contrary this is why they use stainless,it corrodes at a much slower pace than most other materials!!. AND yes,it will corrode eventually! Nothing lasts forever.
Encapsulate a stainless bolt with epoxy,let it cure,throw it in the sea,and I am sure the bolt will long outlast any of us!!
It is watertight and airtight,so nothing will happen until the epoxy is broken down,it gets wet and nature will eventually reclaim what belongs to nature.Too far into the future!!
Isn`t this the reason we encapsulate our boats with fiberglass and epoxy?? To make everything last as long as possible,Not for eternity!
Crevice corrosion is a totally different ballgame,but this will only concern "stuff" put onto the hull on the outside of the protective epoxy layer which will/can get in contact with water.

All the best

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Re: Silicon Bronze vs Stainless

Postby Oyster » Sun Jun 07, 2009 1:52 pm

This topic is always a hot topic. Hardware today is not the same as the by gone era. But also hardware is used differently in boats which can change with building methods. Crevice corrosion is indeed a problem especially in the smaller hardware. But in most cases bolting big timbers or fastening frames to planks in builds that are more traditional using plank on frames, if you can use the Silicon Bronze hardware you are ahead of the game just a bit. The problem now for the states is that there is no longer a foundry fabricating the hardware, only purchasing stock from overseas and cutting the threads. So when you see an advertisement that the bronze is american made, thats exactly what it means unless someone has come along pretty recently which I doubt it.

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Re: Silicon Bronze vs Stainless

Postby jdhogg » Mon Jul 27, 2009 8:49 am

stainless will rust eventully and brass wont last long either,bronze is brass with tin added.i got stainless on my scoot and its rusted after 6 years.i myself am just gonna use whats called for i gotta buy a little at a time but what the heck theres a reason for it

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Re: Silicon Bronze vs Stainless

Postby jbrandt » Mon Apr 16, 2012 3:16 pm

After months of reading, pondering, drinking, and disbelief, I am prepared to add my two cents worth, although my opinions may be worth less to some. Make your own decision... I wont be insulted either way. My opinions are in no way meant to disagree with anyone, nor discount any information or other ideas out there. I have been pondering the use of coated decking screws with lifetime warranties, bronze and stainless. Certainly, regular steel screws would be foolish. I have taked down many decks, and most have had compromised screws (regular as well as deck screws). Plain and simple, deck screws dont hold up on decks. I sure as hell am not putting them in my boat. I have no experience with bronze, but have been more than sasified with the information out there and the previous boat builders who have used bronze. Bronze would be fine by anyones standards. If you think bronze isnt good for boatbuilding, you have no business building a boat. :) Now to the real question: STAINLESS. I have owned over 13 boats in my short 39 years, and have spent countless days weeks and months rebuilding and repairing them. These boats were from the 60's. 70's. 80's and 90's. Yes, all of these vessels (and carcasses) were completely rotted out almost everywhere. One in fact blew the transom out on me as I was 3 miles out in the middle of lake erie. (Fantastic story). I have jars and jars of stainless screws. Jars. I saved every single stainless screw that I took out of those boats, and I took out thousands, especially when I ended up scrapping the hulls. The screws I saved were from windshields, deck rails, and other place that were both wet and dry continuously, definitely exposed to air and water and the sun and snow. I also took out 3" screws that were submerged in rotten transoms for most likely longer than tens of years. Hundreds of screws surrounded by rotting nasty wood. These boats saw most their time on fresh water but some on salt water. I took out screws that were accidentally screwed into gas tanks and left there unknowlingly. Guess what? THEY WERE ALL PERFECT!!! Some had a small amount of "rust" if you willl, but it wiped right off with my fingers. In my humble opinion, stainless is just fine for boatbuilding. I am sure bronze may be better, but perhaps not. If the screws hold up in the worst of conditions for a minimum of 50+ years when boatbuilding was not so great, then I feel more than comfy using stainless in my craft that will be built WAY better. That is my opinion, take it for what it is worth. Im using stainless.

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Re: Silicon Bronze vs Stainless

Postby Andy Garrett » Mon Apr 16, 2012 10:11 pm

Well, since we're reviving a three year old thread, let me chime in on this subject.

I am a knifemaker. I work with a variety of carbon steels and high-carbon stainless steels. The presence of carbon is what allows steel to be hardened for use as a spring or a blade. Mild steels or low carbon stainless steels are softer because they are always in their annealed state (because they cannot be heat treated).

To put it in the simplest terms, stainless steel variety and performance characteristics are as varied as wood species and selecting one suited to boatbuilding needs to be evaluated based on similar criteria. To use a screw for a boat because it says, 'stainless' on the package is a gamble. You want an alloy that is VERY stainless. A harder allow would also prevent stripping heads (a problem I had on more than a few bronze screws).

Iron is an unstable element. It seeks to bond with oxygen (and there's plenty of oxygen in water). We can alloy it with all kinds of stuff to inhibit this characteristic, but in the end, it is still iron.

As for pulling old stainless screws from boats that were perfect, I have no doubt. However, I also feel that quality control of steel back in the day was far better than it is now. Plus, those screws almost certainly came out of Pittsburg or some other big American steel town. Today, we import this crap by the ton from China and other regions where quality control is of a magnitude that allows lead-based paint to be slathered on toys.

I was just watching some of the Titanic anniversary specials yesterday and one thing made me feel good about choosing bronze. They said that when the rest of Titanic was a big orange stain on the bottom of the Atlantic, the giant bronze propellers would still look like they did the day it set sail.
Andy Garrett

Perhaps the slowest Zip build in Glen-L history...

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Re: Silicon Bronze vs Stainless

Postby jamundsen » Tue Apr 17, 2012 5:03 am

i used silicon bronze for everythng below the waterline and stainless above. Where the screw would be buried like on the subdeck I used silicon bronze. There has been some talk that stainless needs air to be really stainless and I dont know how to tell the difference in the stainless available today. I like the stainless on the deck as it looks good.
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Re: Silicon Bronze vs Stainless

Postby Trackhappy » Tue Apr 17, 2012 5:22 pm

Lots of words here already, but a couple things:

1. Brass is NOT suitable. Brass "de-zincafies" in constant contact with water and crumbles away. Make 100% sure through hull fittings are bronze not brass or you will eventually have a gusher.
2. Stainless Steel work hardens and stress cracks so areas where it may flex need to be checked regularly for cracks. A recent example was a Mate's boats bow-eye that parted company due to stress cracking over time.
By the time I have built a boat, I'll be ready to build a boat....

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Re: Silicon Bronze vs Stainless

Postby Old aussie » Wed Apr 18, 2012 5:27 pm

I thought electrolysis was the enemy of all metal in boats that is why we use sacrifical anode blocks......

Old Aussie Peter......

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Re: Silicon Bronze vs Stainless

Postby sean-michael » Thu Jun 07, 2012 6:54 pm

Old aussie wrote:Hi
I thought electrolysis was the enemy of all metal in boats that is why we use sacrifical anode blocks......

Old Aussie Peter......

Expescially in saltwater as I understand it and you have to be particularly carefully mixing fastener materials.

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Re: Silicon Bronze vs Stainless

Postby Alain2 » Fri Aug 16, 2013 8:32 am

Electrolysis: chemical change in a solution (or electrolyte) by the passage of electric current.

Electrolysis is used to produce oxygen in a submarine for example. It has nothing to do with boat and corrosion.
What you are referring to is;
1- galvanic corrosion, electrochemical reaction between two different metals.
2- electrolytic corrosion, corrosion of metal associated with the flow of electrical current in an electrolyte.



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Re: Silicon Bronze vs Stainless

Postby Cyclone » Fri Aug 16, 2013 2:46 pm

I was glad I used silicon bronze when I hit some screw heads with a power planer when fairing. I thought I sunk them deep enough, but I found out otherwise. I was also able to use my rasp in areas with some contact to screw heads. If these screws were stainless it would have been a problem.

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Re: Silicon Bronze vs Stainless

Postby falconer100 » Sun Oct 06, 2013 4:08 pm

Just to confuse matters, what about the new Duplex stainless steel which are at least 50% harder than 316?

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