Reply
 
Thread Tools Search this Thread Display Modes
 
Old 11-10-2018, 07:04 PM   #1
Senior Member
 
City: Lutz
Country: USA
Join Date: Jan 2016
Posts: 444
Stainless with Bronze in Salt Water

My new-to-me 1982 Marine Trader DC has a hodgepodge of stainless metal combined with Bronze. For example-the PO had the prop shaft tunnel pipe replaced with 316 stainless pipe. Its screwed into bronze stuffing box one end and bronze cutlass bearing fitting on the other end , the packing bronze fitting is held together with 2 stainless bolts, the swim platform is held by bronze fittings with stainless steel pipes 45 degrees at the hull-- they usually are underwater, the seacocks are bronze with stainless steel bolts holding them to the hull. Oh yes -the rudder is stainless steel with a bronze packing fitted into a mild steel structural fitting. This long time sailor asks: Is this typical in the Trawler world?? Thanks anyone
__________________
Advertisement

geoleo is offline   Reply With Quote
Old 11-11-2018, 07:24 AM   #2
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 19,730
Many early TT (and lots of later) ones were put together with what was on hand at the local hardware store..

Except for some commercial fish boats , boating was illegal in that era so a knowledge base did not exist , and cost was always a factor.

Up grading with silicon bronze bolts , etc, is what most owners have done over the past 20-40 years.
__________________

FF is offline   Reply With Quote
Old 11-11-2018, 08:03 AM   #3
Senior Member
 
City: Lutz
Country: USA
Join Date: Jan 2016
Posts: 444
The stainless steel prop tube and cutlass and shaft log replacements was done by Marsh Harbor Boat Works in SC. The PO said the stern cutlass brg holder "somehow came loose" and wore a hole in the original fiberglass prop tube holder. I suspect the brg holder "came loose" due to a ss bolt or bolts holding the cutlass bearing breaking due to being weakened by electrolysis.
geoleo is offline   Reply With Quote
Old 11-11-2018, 09:16 AM   #4
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,681
I had SS rudders, SS shafts, and basically all else was SB or manganese bronze u/w. Boat was 24/7/12 in the warm salt. The issues i did see were with the small SS screws holding shaft logs in, and the garboard fitting. Here, both SS crevice corrosion was at work, along with some galvanics that slowly dissolved some SS screw heads. Also saw some pitting corrosion on the shaft at the stuffing. All this stuff was years and years in the making, and not a huge issue, overall.
diver dave is offline   Reply With Quote
Old 11-11-2018, 11:34 AM   #5
DDW
Guru
 
City: San Francisco
Country: USA
Join Date: Apr 2018
Posts: 920
One problem with SS set screws and bolts, the commonly available grade is 304 which is less resistant to chloride corrosion than 316. The latter grade is available from McMaster Carr or other big industrial houses. The problem with "bronze" in today's market is it pretty much all comes from China, and might be called "silicon bronze" or "manganese bronze" when it isn't really. It takes a laser spectrometer to be able to tell for sure. Cutlass bearing bodies aren't even claimed to be bronze, but rather brass. If you keep zincs on everything in good shape, galvanic corrosion should be minimized, replacing the 304 SS with 316 will help with crevice corrosion but not eliminate it.
DDW is offline   Reply With Quote
Old 11-11-2018, 11:52 AM   #6
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,681
Good boat yards aught to have one of these, which I had my company buy:
https://www.thermofisher.com/order/catalog/product/XL2

Takes about 15 seconds to get a non-destructive good read on aluminum, steel, copper alloys, much more.

Very popular with scrap metal yards.
diver dave is offline   Reply With Quote
Old 11-11-2018, 12:39 PM   #7
Veteran Member
 
AKFish's Avatar
 
City: Seward, AK
Country: USA
Vessel Model: Custom 45' Steel Trawler
Join Date: Sep 2013
Posts: 74
Quote:
Originally Posted by diver dave View Post
Good boat yards aught to have one of these, which I had my company buy:
https://www.thermofisher.com/order/catalog/product/XL2

Takes about 15 seconds to get a non-destructive good read on aluminum, steel, copper alloys, much more.

Very popular with scrap metal yards.

From the website's "Request a Quote" form, it looks like it takes a bit of unobtainium to purchase one of these analyzers.
AKFish is offline   Reply With Quote
Old 11-11-2018, 12:46 PM   #8
Guru
 
psneeld's Avatar
 
City: AICW
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 19,974
Arent there a few bronzes that have common names that include brass?

Like Naval Brass and Red Brass that are also known as bronze and formulated to avoid dezincafication?
psneeld is offline   Reply With Quote
Old 11-11-2018, 12:51 PM   #9
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,681
Quote:
Originally Posted by AKFish View Post
From the website's "Request a Quote" form, it looks like it takes a bit of unobtainium to purchase one of these analyzers.
I recall about $10k or so; 4 years ago.
diver dave is offline   Reply With Quote
Old 11-11-2018, 01:02 PM   #10
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,681
Quote:
Originally Posted by psneeld View Post
Arent there a few bronzes that have common names that include brass?

Like Naval Brass and Red Brass that are also known as bronze and formulated to avoid dezincafication?
"naval" about 39% zinc. "red" takes Zn down to about 15%.

I can send an excel via email upon request. I have tensile strength, and composition for a number of marine alloys, including Al, and steel, etc. But, I do notice some pretty small elements added can make some big physical changes. For instance, the 1 to 4% of silicon added to pure copper (to make silicon bronze) makes its electrical conductivity 10 to 15 x worse.
diver dave is offline   Reply With Quote
Old 11-11-2018, 03:27 PM   #11
DDW
Guru
 
City: San Francisco
Country: USA
Join Date: Apr 2018
Posts: 920
"Bronze" is a very slippery word today. It used to mean tin and copper alloyed perhaps with a few other things to improve strength. There are lots of things called bronze that aren't these days. Add to that the stuff being sold specifically as silicon bronze that isn't.

The laser spectrographs are a really neat tool, but a bit out of the impulse buy price point. It would be interesting to wonder down the isle a the local West Marine and shoot some of the "bronze" fittings and hardware. I keep looking for a cheap used one on ebay, no luck yet.
DDW is offline   Reply With Quote
Old 11-11-2018, 03:38 PM   #12
Guru
 
psneeld's Avatar
 
City: AICW
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 19,974
Naval Brass refers to a copper alloy of around 59% Copper 40% Zinc and 1% Tin with a trace amount of Lead. This alloy falls into the subfamily for Brasses known as Alpha Beta or Duplex Brasses. These Alpha Beta Brasses are generally harder and stronger than other non-Alpha Beta Brasses.

As its name implies, Naval Brass was originally developed for sea water service applications. Tin in included in the alloy composition in order to improve the corrosion resistance of Naval Brass. The presence of lead in Naval Brass assists in the machinability of the metal. C464 Naval Brass Rod has a fair machinability with about 35% of Free Machining Brass.

The addition of Tin also gives Naval Brass a high resistance to dezincification. Dezincification is a type of dealloying in which one of the constitutes of an alloy is removed by corrosion. Dezincification was first recognized as a serious problem in brass tubes used for ship condensers around 1920. At the time this problem was referred to as “Condenseritis”. Since then various alloys have been formulated to stop this process, one of which being Naval
Brass.

Http://www.nationalbronze.com/News/what-is-naval-brass/
psneeld is offline   Reply With Quote
Old 11-11-2018, 04:39 PM   #13
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,681
Both California and the EU now are putting up a fuss with lead in anything, even when alloyed. We have had to deal with Al without copper, and brass without lead for a multitude of products for a couple years now.
Nickel is a now a target too.

DDW; that tool I referenced has an X ray source for the exciter. We also have a FTIR, which uses, I believe, a small IR laser source. That we use for elastomeric/plastic/rubber analysis.
__________________

diver dave is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 06:08 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×