bronze or brass screws?

[James_D]

Some of the Bronze screws broke off whilst removing them and I wonder if they could be replaced with brass? What are pros and cons? thank you JD

 

[johnlilley]

Hi there, brass or bronze?
I am assuming these are below the waterline and perhaps plank fastenings?

If that is the case you would be strongly advised to use bronze as against brass, brass are much more likely to shear when tightened to the same torque as bronze, but more importantly brass will quickly dezincify below the waterline in salt water and structurally fail within a few seasons. Stainless is unpredictable below the waterline and not absolutely reliable, although above the waterline probably fine as might be brass although still not fully reliable due to corrosion (dezincification) but larger dia. brass is less susceptible to failure, but bear in mind the lower strength of brass.

John Lilley

 

[Porthandbuoy]

Bronze is the more noble metal and should be used where the wood may be wet. ie. securing planks to frames. Brass is generally OK for interior joinery.
St/st tends to be a bit unpredictable, as mentioned above, in that it is only stainless by virtue of an oxide coating. Put st/st in a corrosive environment where with very little or no oxygen, such as a lump of wet wood, it can disappear very quickly. In all cases it is essential to drill the pilot and clearance holes to the correct diameter if the full strength of the fastening is to be achieved.

 

[roly_voya]

I have had a fair amount of experience of removing old screws from 60's 70's boats and based on this would say NEVER USE BRASS. All the brass scews have brocken on removal and many have clearly corroded. If you are making a fastening that never needs to be undone (eg when glued as well) bronze boat nails are about the same price as brass screws. For areas that might be wet bronze is the only option. In dry wood I have not had problems with S/S. A good trick for all screws you want to be able to remove later is to dip them in Lanocote before screwing in, helps stop them ceasing in and may give extra corrosion protection.

 

[cliffordpope]

I think "bronze" covers a wide variety of alloys, some of which are little better then brass. At the other end, silicon bronze and others are corrosion resistant and easily as strong as steel.
Iron makes a pretty good nail. The chinese method was to heat to red heat and dip into a pan of pitch or tar. Ancient junks on breaking up have been found to have uncorroded nails.
Proper galvanised screws have had their following.

 

[roydymond]

Yes we have used the same method of heating iron nails and dipping into tar in the old days. As for brass screws its completely wrong to use these on the hull and bronze is correct. Although theres much to consider about fastenings, there is nothing to consider about brass anywhere on the hull. Its only good for interior linings and even then we are always removing duff brass screws inside older boats and replacing with stainless especially around humid areas.
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[ccscott49]

I will not use brass screws anywhere on a boat, even inside, IMHO they have no place aboard. Bronze (silicon) or A4 stainless, nothing else. In screws anyway! Copper roves and nails, copper tacks, bronze ring nails.

 

[stevemeakin]

just to chuck my bit in...there is brass that is as good as Silcon bronze although I doubt you'll get hold of it - Admiralty Brass /forums/images/graemlins/blush.gif)

 

[ccscott49]

Admiralty brass?? as good as silicon bronze?? You´ll have to clarify that one I´m afraid, if it has zinc in it, then it can dezinc?

 

[whiteoaks7]

The 'Admiralty' (MoD N) has banned brass fittings for the reasons given and this includes gunmetal / admiralty brass. The only bronze I know they use is nickel-ali-bronze (NAB) which is ok underwater. The worst environment is salt spray (and warm salt spray at that) so if your fittings are in that zone you have a tough problem. The admiralty also dissallows stainless (even 316) on submarines now, and relies on either well treated carbon steel (ie lots of good paint) or super duplex stainless steels, which are horrendously expensive and difficult to machine. I suggest you try to get some NAB.

 

[James_D]

many thanks all for advice, stainless it is! on removing the old white D fendering some of the bronze screws broke off which held it in place. jd.

 

[Niander]

If i was screwing into ribs from the outside of the hull below waterline would stainless be ok...or wouldnt they get enough oxygen after antifoul?
bronze best ?

 

[ccscott49]

Bronze, but it also depends on what the other fastenings are.

 

[Niander]

Bronze it is then what sealer would i dip them in below water line ?

 

[ccscott49]

I would use lanolin (lanocote).

 

[skenn_ie]

Can anyone recommend a source of bronze fasteners ?. I have a bunch of studs and bolts de-zincified, albeit on a 50y/o vessel. These are in water pumps, and heat exchangers ... some crumble in the hand. I am particularly looking for 3/4" Whitworth studs & (ideally)capnuts, and 1/4" A/F bolts

 

[Seanick]

Anglia Stainless aka Combwich marine Enterprises stock what you need.