Silicon Bronze Material

[classicboats turkiye]

I would like to open new discussion:
We decided to start to build 2 units of Blue Moon .
Building methode will be cedar planking on laminated frames and keel on oak.
We want to use SILICON BRONZE fastgrip nails and screws on planking.
Mounting of outside ballast of 1.040kg made by cast iron should be fastened by 1/3" galvanised bolts.

1- what is the compatibility of silicon bronze with other metal materials?
2- on wich areas could we use silicon bronze materials (under WL)?

Please discuss the matter

[Lewisboats]

Excerpted from Corrosion Doctor's Web page
Galvanic Series in Seawater
A galvanic series has been drawn up for metals and alloys in seawater, which shows their relative nobility. The series is based on corrosion potential measurements in seawater. The relative position of the materials can change in other environments. The further apart the materials are in this series, the higher the risk of galvanic corrosion. (reference)

Most cathodic, noble, or resistant to corrosion
Platinum
Gold
Graphite
Titanium
Silver
Chlorimet 3
Hastelloy C
18-8 Mo stainless steel (passive)
18-8 stainless steel (passive)
Chromium steel >11 % Cr (passive)
Inconel (passive)
Nickel (passive)
Silver solder
Monel
Bronzes
Copper
Brasses
Chlorimet 2
Hastelloy B
Inconel (active)
Nickel (active)
Tin
Lead
Lead-tin solders
18-8 Mo stainless steel (active)
18-8 stainless steel (active)
Ni-resist
Chromium steel >11 % Cr (active)
Cast iron
Steel or iron
2024 aluminum
Cadmium
Commercially pure aluminium
Zinc
Magnesium and its alloys
Most anodic or easy to corrode





So...as you can see, your bronze nails and screws will eat away at your keel and keel bolts. You should use galvanized nails and screws or switch your keel to Lead and Silicon Bronze bolts to go with bronze nails and screws. For cost wise go with the cast iron and steel but for resale value go with lead and bronze.

[donald branscom]

I would like to open new discussion:
We decided to start to build 2 units of Blue Moon .
Building methode will be cedar planking on laminated frames and keel on oak.
We want to use SILICON BRONZE fastgrip nails and screws on planking.
Mounting of outside ballast of 1.040kg made by cast iron should be fastened by 1/3" galvanised bolts.

1- what is the compatibility of silicon bronze with other metal materials?
2- on wich areas could we use silicon bronze materials (under WL)?

Please discuss the matter


"We decided to start to build 2 units of Blue Moon ."
Did you mean two boats? Never heard of a boat called a "UNIT"

With a lead keel:
1.**copper,**~-0.3 to -0.37V (sacrificial metal)
2.**410/416 stainless (passive) Ferritic, ~-0.23 to -0.35V
3.**silicon bronze, ~-0.25 to -0.29V
4.**nickel aluminium bronze. ~-0.14 to -0.22V
So 316 stainless would be a better choice.

Cast iron and bronze are not compatable because there is too much of a difference. High copper content. The keel would be sacrificed. A lead keel would be better. Where would you get cast iron these days?
copper and steel or iron is not a good combo.

Many power boats use bronze fastenings but of coarse they do not usually have much of a keel. If it was me i would ask a boat yard worker that is very experienced what they think from what they have seen.

If you do use a cast iron keel why not just use high grade steel bolts?
The only problem will be bronze near the cast iron keel, the bronze fastenings would be higher on the galvanic scale.

The best bolts with cast iron keel would be 2024 T4 Aluminum bolts.

[donald branscom]

This would be my choice for a cast iron keel.

Cast iron keel. High grade steel bolts. galvinized steel fastenings.

The aluminum 2024 T4 bolts will be VERY expensive,hard to get and the High grade steel bolts will be VERY easy to get and inexpensive.

[Gary E]

Why in this day and age would anyone use steel or so called iron fastenings even if they are galvanized.
Using galvanized carriage bolts to hold major items may be ok, but SiBrz is a much better choise. More expensive to start with, but I spose it depends on your planned ownership time and your wallet.

All you have to do is look at all the old hulls painted red...that's not cuz they like red,
it's to hide the rust stains running down the sides.

Do you sailboat guys put zincs on underwater metal parts?

[Bob Cleek]

You really should look long and hard at going with a lead keel. Given the cost of iron castings and the entire electrolytic issue, lead, with bronze keel bolts, is easier and less expensive in the long run. Also, you can pour it yourself. Iron bolts aren't what they used to be, galvanized or not. True "wrought iron" corrodes far less than steel. Bronze should last the life of the boat, absent its being cooked by stray current. Blue Moon is a small boat and there really isn't any economy to be had in cutting corners on materials.

[donald branscom]

Why in this day and age would anyone use steel or so called iron fastenings even if they are galvanized.
Using galvanized carriage bolts to hold major items may be ok, but SiBrz is a much better choise. More expensive to start with, but I spose it depends on your planned ownership time and your wallet.

All you have to do is look at all the old hulls painted red...that's not cuz they like red,
it's to hide the rust stains running down the sides.

Do you sailboat guys put zincs on underwater metal parts?

YES,Sailboats have zinks.
Steel hulls have zinks
Wood boats use zinks.
Fiberglass boats use zinks.
Aluminum boats have zinks.

[Roger Cumming]

My first boat was a Dragon class sloop built in Denmark, with a cast iron keel and bronze plank fastenings. The boat was almost 20 years old when I got her. The plank fastenings were in good condition. The cast iron ballast keel was rusty but every year it got a new coat of bottom paint and, being under water did not detract from the boat's appearance. I had several zincs, one on the rudder which I renewed each year. I do not know what the keel bolts were made of - probably steel. They were not high on the list of things to do. The electrolysis that was presumably taking place caused the ton of cast iron ballast keel to rust a little faster than if there were no bronze fasteners nearby.

The suggestion to use galvanized fastenings seems wrong from my experience. The only detriment to the cast iron keel is the corrosion it suffers but this is mainly a cosmetic problem. It would corrode in sea water without the bronze plank fasteners. Cast iron imparts strength to the boat. The late Bud McIntosh preferred cast iron keels to lead.

If there is an economic reason to use cast iron instead of lead for the keel, there is no reason not to do it. And of course the hull fastenings should be bronze.

[TMny]

>The best bolts with cast iron keel would be 2024 T4 Aluminum bolts.

From "The Boatowner's Guide to Corrosion", Everett Collier, (C)2001 , International Marine/McGraw-Hill; Chapt9, 'Aluminum and Aluminum Alloys':
-pg76, "The alloys of primary interest to us for marine use are the 5000 and 6000 series."
-pg77, '2000 Series Wrought Alloys (A92XXX) and Casting Alloys (AO2XX.X)
"Copper is the major alloying element in the 2000 series. Corrosion resistance is not as good as most other aluminum alloys and tends to worsen over time as galvanic cells are created by the tiny copper particles deposited on the surface as a result of the corrosion process. Alloys of this group , including those clad with a more corrosion-resistant alloy--called alclads-- are not suitable for marine applications."
* * *
{Among wrought aluminums, 5052,5083,5086,5456,5454, and the commonly extruded 6061 exhibit good corrosion resistance in marine environments , and are regularly used in boatbuilding.}

* * * * * * * * *
The silicon bronze alloy has proved to last a very long time in marine service, Everdur is an excellent wood fastening material , above and below waterline in brine.

As noted above, copper-based alloys (including bronzes and brasses) are not suited for fastening to cast iron below the waterline, or elsewhere in marine atmospheres/brine.

Again, as noted above , galvanised steel fastenings are compatible with cast iron keels ; modern galvanising is of lesser quality than that of yore , due largely to environmental restrictions. "Galvanising" consists of a zinc coating; for marine applications it should be "hot dipped" , rather than the much thinner "elecrogalvanising"....

Stainless steel {'SS'} alloy316 is a tolerable fastening material for securing cast iron keels. For a trailered boat that doesn't spend more than a couple weeks at a time in the drink, it is more than adequate. In freshwater, (and possibly cold brackish water) it would be OK.
Better castiron keelbolt-fastening material choices for constant immersion in brine proximate the equator would be "superduplex" , or "superaustenitic" stainless steel alloys {or some more exotic alloys}.

Either galvanised steel or SS316 woodscrews would be suitable for fastening ribs/garboards/floors to a cast iron keel. Galvanic corrosion only occurs between different metals in contact; it is permissible to use silicon bronze screws for the planking except where planks are screw-fastened into the keel (where SS316/galvanised), as long as the silicon bronze does not contact either the cast iron , galvanised , or stainless steel !!
T m

[Oscarvan]

. Galvanic corrosion only occurs between different metals in contact

Or if they are both immersed in the same conductive medium (scientific term for salt water...) right?

[Roger Cumming]

Right.

[TMny]

>Posted by: Oscarvan
>On: 09-14-2007 05:35 AM
>---Quote---
> Galvanic corrosion only occurs between different metals in contact
---End Quote---
>Or if they are both immersed in the same conductive medium (scientific term for salt water...) right?

--NEGATIVE , generally. From Everett Collier, (C)2001 (same source), pg 18:
"Galvanic corrosion involves two or more dissimilar metals, by which I mean metals widely separated in the galvanic table--mild steel and bronze , for example. The metals must be connected by a metallic path--either by direct physical contact or by a conductor--and must be in contact with the same body of electrolyte."

It is technically allowable (regarding galvanic corrosion, only) to mix fastenings of different metallic alloys when securing one piece of wood to another. It is reasonable to be deliberate in the choice of materials making contact in solution when they are metallic , and not the same alloy.

As a practical matter if old planks have been fastened to ribs with iron , and the refastening is to involve bronze , it may well pay to remove iron remnants. But technically there will not be any galvanic corrosion if the distinct fastenings don't make contact (and aren't wired together).

Google helps reinforce:
http://www.assda.asn.au/asp/index.asp?pgid=18533
http://www.corrosion-club.com/galvanic.htm
http://www.ocean.udel.edu/seagrant/publications/corrosion.html
http://www.key-to-steel.com/Articles/Art160.htm
http://www.engineersedge.com/corrosion/galvanic_corrosion.htm

[Jay Greer]

I have worked on quite a few boats that were built back in the thirties and twenties that were ballasted with iron and fastened with galvanized iron boat nails. The oldest was built in 1907. Granted all of these boats receintly went through complete re-builds but they all lasted seventy years or more before total restoration was necessary.
On the other hand, I prefer lead keels and bronze or monel fastenings purely due to the fact that they create fewer problems and obviate the constant attention needed when dealing with rust intrusion.
On the side of lead ballast; it, being heavier than iron, lowers the center of gravity of the vessel which is a definate plus. Additionally it is kinder to a hull if the vessel should take a hard grounding, often allowing the boat to escape major damage due to the shock absorbing qualities of the material.
Jay

[classicboats turkiye]

I would like to thank for avery comments according to chosing fastening systemes.