HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Comments
View Comments: Newest First|Oldest First|Threaded View
<<  <  Page 2/2
Dave Palmer
User Rank
Platinum
Brass, bronze, and dezincification
Dave Palmer   3/29/2012 3:49:12 PM
NO RATINGS
1 saves
Brass and bronze are two different things.  Brass is an alloy of copper and zinc.  Bronze is usually an alloy of copper and tin -- although there are also aluminum bronzes, manganese bronzes, and silicon bronzes, which are alloys of copper with aluminum, manganese, or silicon, respectively.  Each of these catagories (brass, bronze, aluminum bronze, etc.) includes many different alloys with different properties.

I'm not quite sure what "shop brass" is, but cheap screw machined parts are often made out of free-machining brass (UNS C36000).  This is an alloy of copper, zinc, and lead.  The lead helps to make it readily machinable.

As the article correctly points out, copper and zinc are very far apart in the galvanic series, so when a brass part is exposed to a good electrolyte (like seawater), the zinc acts as a sacrificial anode for the copper.  Ultimately, all of the zinc dissolves out of the brass, leaving a spongy mass of copper with very little strength.  I'm willing to bet that if your uncle looked at the failed part under a microscope, he would have seen this sponge-like structure.  This process is called dezincification.

Naval brass is a type of brass (usually approximately 60% copper, 40% zinc) which also contains a small amount (0.5 - 0.8%) of tin.  Small amounts of arsenic, phosphorus, or antimony might also be added.  The presence of these elements help to inhibit dezinicification.

The absolute best copper alloys for saltwater service are copper-nickel alloys.  These alloys have excellent corrosion resistance.  However, they also tend to be fairly expensive.

This article is a good example of why proper materials selection is so important.  It pays to do your homework -- or, better still, ask a metallurgist.

Rob Spiegel
User Rank
Blogger
Re: Small component, big damage
Rob Spiegel   3/29/2012 3:43:30 PM
NO RATINGS
Bob from Maine, it sounds like you'[re suggesting this may not be a Made by Monkeys problem but rather a simple wear-and-tear-over-many-years problem. Are there ways to check this before it causes a serious accident?

bob from maine
User Rank
Platinum
Re: Small component, big damage
bob from maine   3/29/2012 3:38:23 PM
NO RATINGS
Don't know how long you'd had this boat, but Cheoy Lee Clippers were made in the 50's and 60's, so this incident could be due to simple age. My experience with Cheoy Lee has been their hardware is of very high quality and their hulls of that era were quite over-built. Most "Bonze" shafts, propellors, seacocks, and general fittings have some zinc, though I can't remember the exact percentage. Boats that spend time at the dock, particularly where other boats have shore-power plugged-in have a tendancy to de-zinc many of their bronze underwater fittings due to stray eddy current in the water. Also the Dolphin Striker assembly is usually not disassembled during winter storage so is never checked and unfortunately is a fairly common point of failure for this reason.

Rob Spiegel
User Rank
Blogger
Small component, big damage
Rob Spiegel   3/29/2012 9:48:46 AM
NO RATINGS
It's amaging the damage a small weak component can do. I wojld imagine there may be liability issues with this accident.

<<  <  Page 2/2


Partner Zone
Latest Analysis
It's been two years since the Mac Mini's last appearance on iFixit's teardown table, but a newly revised version joins Apple's lineup this week.
More often than not, with the purchase of a sports car comes the sacrifice of any sort of utility. In other words, you can forget about a large trunk, extra seats for the kids, and more importantly driving in snowy (or inclement) weather. But what if there was a vehicle that offered the best of both worlds; great handling and practicality?
Kevin Gautier of Formlabs describes the making of a carbon fiber mold for an intake manifold, using a $3,300 3D printer, during Medical Design & Manufacturing Midwest.
Science fiction author Isaac Asimov may have the best rules for effective brainstorming and creativity. His never-before-published essay, "On Creativity," recently made it to the Web pages of MIT Technology Review.
Much has been made over the potentially dangerous flammability of lithium-ion batteries after major companies like Boeing, Sony, and Tesla have grappled with well-publicized battery fires. Researchers at Stanford University may have come up with a solution to this problem with a smart sensor for lithium-ion batteries that provides a warning if the battery is about to overheat or catch fire.
More:Blogs|News
Design News Webinar Series
10/7/2014 8:00 a.m. California / 11:00 a.m. New York
9/25/2014 11:00 a.m. California / 2:00 p.m. New York
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Oct 20 - 24, How to Design & Build an Embedded Web Server: An Embedded TCP/IP Tutorial
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: 10/28-10/30 11:00 AM
Sponsored by Stratasys
Next Class: 10/28-10/30 2:00 PM
Sponsored by Gates Corporation
Next Class: 11/11-11/13 2:00 PM
Sponsored by Littelfuse
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service