5 ms·

Sounds like they got a bad batch of steel or something. Corrosion doesn't cause steel to become brittle. It weakens it, yes, but it does so by reducing the cr

Sounds like they got a bad batch of steel or something. Corrosion doesn't cause steel to become brittle. It weakens it, yes, but it does so by reducing the cross-section. Corrosion doesn't materially alter the bulk properties of the metal, only the amount of metal in the bulk. I get that there's corruption and shortcuts getting taken everywhere on big projects like this. But it's still surprising that better QA/QC isn't done. There's going to be a lot of finger pointing on whose fault this is.

devindotcom 11y ago
Yeah, I can imagine lax quality control if you're making... I don't know, a desk or even a house, but a bridge? Whoever dropped the ball put a HELL of a lot of people (and money) in jeopardy - even if the corrosion isn't going to critically affect the structure, it makes one wonder about the quality of the rest of the materials, and the contracts involved...
- Dav3xor 11y ago
  And for people who've never been to San Francisco -- this bridge is a huge huge thing, and any problems with it are a very big deal.
  - x0x0 11y ago
    $6.4B and counting, plus a quarter million vehicles per day; there is no possible alternate way to move that many people. It had to be replaced while the old one was still used.
    - simulate 11y ago
      Since drivers pay the $6 toll only one direction, it will take $6.4B / (125,000 vehicles per day * $6 per car * 365.25 days per year) = 24 years to pay off the bridge with tolls alone.
      - aggie 11y ago
        With a projected lifespan of 150 years [1], that seems pretty reasonable. [1] http://www.dot.ca.gov/dist4/eastspans/ http://www.dot.ca.gov/dist4/eastspans/
- oh_sigh 11y ago
  Well, the construction of the bridge decks and the materials for the bridge was made in China...
  - sneak 11y ago
    So are Apple Watches and iPads. Please stop it with this nonsensical nationalism/racism.
    - x0x0 11y ago
      It's well known that china has lax safety and quality standards. See for one of many examples the adulterated pet food from china or the milk scandal where china poisoned 300,000 infants [1]. To this day, China's own citizens import milk for their children if they can [2]. Or chinese drywall [3]. It's merely prudent to safety test food and materials imported from China. [1] http://en.wikipedia.org/wiki/2008_Chinese_milk_scandal http://en.wikipedia.org/wiki/2008_Chinese_milk_scandal [2] http://www.bloomberg.com/bw/articles/2014-11-16/china-turns-to-the-u-dot-s-dot-and-australia-to-import-safer-milk http://www.bloomberg.com/bw/articles/2014-11-16/china-turns-... [3] http://en.wikipedia.org/wiki/Chinese_drywall http://en.wikipedia.org/wiki/Chinese_drywall
      - prewett 11y ago
        China also has had a bunch of spectacular construction failures. My favorite is the Shanghai bridge made out of styrofoam and garbage [1], but there are other, less spectacular examples: [2]. The schools in Sichuan are notable for poor construction, as many schools feel down but adjacent buildings did not. [3] Apparently one builder would tap the cement on inspection, and if it didn't ring right, he would make the contractor redo it. They didn't like him much, but his schools stayed up. Can't find the article, though. Apparently the rebuilding isn't any better [4]. I wouldn't even consider using Chinese construction material. [1] http://www.weirdasianews.com/2010/02/05/shanghai-wonderbridge-trash-collapses/ http://www.weirdasianews.com/2010/02/05/shanghai-wonderbridg... [2] http://world.time.com/2012/08/27/bridge-collapse-in-china-raises-questions-about-safety-of-countrys-road-construction-boom/ http://world.time.com/2012/08/27/bridge-collapse-in-china-ra... [3] http://www.nytimes.com/2008/05/25/world/asia/25schools.html?pagewanted=all http://www.nytimes.com/2008/05/25/world/asia/25schools.html?... [4] http://www.npr.org/sections/parallels/2013/05/14/183635289/Five-Years-After-A-Quake-Chinese-Cite-Shoddy-Reconstruction http://www.npr.org/sections/parallels/2013/05/14/183635289/F...
- gscott 11y ago
  The bridge was made in China and assembled here. There were a lot of quality control and cost overrun issues. The Chinese company would kick out the American inspectors.
  - MrBuddyCasino 11y ago
    The bolts in question were made by an american company. The same issue happened with another bridge before. See https://news.ycombinator.com/item?id=9695276 https://news.ycombinator.com/item?id=9695276
VLM 11y ago
Possibly the journalist mixed two totally separate stories, hydrogen embrittlement and corrosion fatigue. That would fit the symptoms and the journalists visual observations of testing. I suppose H2 damaged steel, could lead to cracks, that when put underwater under tension would cause faster than expected corrosion fatigue like a couple years instead of a couple centuries, they're not totally unrelated. (edited to rephrase corrosion doesn't cause brittleness but brittleness can speed corrosion in the above scheme)
- benzofuran 11y ago
  Not knowing the particulars of the bridge CP system in place, hydrogen embrittlement is possible but it sounds more like stress corrosion cracking is the major culprit.
  - refurb 11y ago
    Where would the hydrogen come from in a situation like this? I know aluminum will produce hydrogen under basic or acid condition, but steel doesn't (I think).
    - Someone 11y ago
      I think from a reaction 2Fe + 3H2O -> Fe2O3 + 3H2 See http://www.madsci.org/posts/archives/2005-12/1134348446.Ch.r.html http://www.madsci.org/posts/archives/2005-12/1134348446.Ch.r...
benzofuran 11y ago
This sounds like a poster child for stress corrosion cracking - which would greatly impact the toughness of the material. Most steels (including stainless) become significantly more brittle under stress when exposed to high chloride environments like seawater while under load - much more than standard fracture mechanics would suggest. Basically there's chloride penetration and then hydrogen generation at the grain boundaries within the metal structure, which significantly reduces the toughness and allows for rapid and catastrophic failure easily.
krschultz 11y ago
Actually that's not 100% correct. Most steel is not at risk, but some forms of high strength steel are susceptible to hydrogen embrittlement in salt water. I don't have enough info to comment on this case, and I don't trust the article because the author can't even get stress vs strain right, but it could be the problem here.
jacquesm 11y ago
Galvanic corrosion can cause steel to become brittle. http://en.wikipedia.org/wiki/Hydrogen_embrittlement http://en.wikipedia.org/wiki/Hydrogen_embrittlement

devindotcom 11y ago

Yeah, I can imagine lax quality control if you're making... I don't know, a desk or even a house, but a bridge? Whoever dropped the ball put a HELL of a lot of people (and money) in jeopardy - even if the corrosion isn't going to critically affect the structure, it makes one wonder about the quality of the rest of the materials, and the contracts involved...

Dav3xor 11y ago
And for people who've never been to San Francisco -- this bridge is a huge huge thing, and any problems with it are a very big deal.
- x0x0 11y ago
  $6.4B and counting, plus a quarter million vehicles per day; there is no possible alternate way to move that many people. It had to be replaced while the old one was still used.
  - simulate 11y ago
    Since drivers pay the $6 toll only one direction, it will take $6.4B / (125,000 vehicles per day * $6 per car * 365.25 days per year) = 24 years to pay off the bridge with tolls alone.
    - aggie 11y ago
      With a projected lifespan of 150 years [1], that seems pretty reasonable. [1] http://www.dot.ca.gov/dist4/eastspans/ http://www.dot.ca.gov/dist4/eastspans/
oh_sigh 11y ago
Well, the construction of the bridge decks and the materials for the bridge was made in China...
- sneak 11y ago
  So are Apple Watches and iPads. Please stop it with this nonsensical nationalism/racism.
  - x0x0 11y ago
    It's well known that china has lax safety and quality standards. See for one of many examples the adulterated pet food from china or the milk scandal where china poisoned 300,000 infants [1]. To this day, China's own citizens import milk for their children if they can [2]. Or chinese drywall [3]. It's merely prudent to safety test food and materials imported from China. [1] http://en.wikipedia.org/wiki/2008_Chinese_milk_scandal http://en.wikipedia.org/wiki/2008_Chinese_milk_scandal [2] http://www.bloomberg.com/bw/articles/2014-11-16/china-turns-to-the-u-dot-s-dot-and-australia-to-import-safer-milk http://www.bloomberg.com/bw/articles/2014-11-16/china-turns-... [3] http://en.wikipedia.org/wiki/Chinese_drywall http://en.wikipedia.org/wiki/Chinese_drywall
    - prewett 11y ago
      China also has had a bunch of spectacular construction failures. My favorite is the Shanghai bridge made out of styrofoam and garbage [1], but there are other, less spectacular examples: [2]. The schools in Sichuan are notable for poor construction, as many schools feel down but adjacent buildings did not. [3] Apparently one builder would tap the cement on inspection, and if it didn't ring right, he would make the contractor redo it. They didn't like him much, but his schools stayed up. Can't find the article, though. Apparently the rebuilding isn't any better [4]. I wouldn't even consider using Chinese construction material. [1] http://www.weirdasianews.com/2010/02/05/shanghai-wonderbridge-trash-collapses/ http://www.weirdasianews.com/2010/02/05/shanghai-wonderbridg... [2] http://world.time.com/2012/08/27/bridge-collapse-in-china-raises-questions-about-safety-of-countrys-road-construction-boom/ http://world.time.com/2012/08/27/bridge-collapse-in-china-ra... [3] http://www.nytimes.com/2008/05/25/world/asia/25schools.html?pagewanted=all http://www.nytimes.com/2008/05/25/world/asia/25schools.html?... [4] http://www.npr.org/sections/parallels/2013/05/14/183635289/Five-Years-After-A-Quake-Chinese-Cite-Shoddy-Reconstruction http://www.npr.org/sections/parallels/2013/05/14/183635289/F...
gscott 11y ago
The bridge was made in China and assembled here. There were a lot of quality control and cost overrun issues. The Chinese company would kick out the American inspectors.
- MrBuddyCasino 11y ago
  The bolts in question were made by an american company. The same issue happened with another bridge before. See https://news.ycombinator.com/item?id=9695276 https://news.ycombinator.com/item?id=9695276

VLM 11y ago

Possibly the journalist mixed two totally separate stories, hydrogen embrittlement and corrosion fatigue. That would fit the symptoms and the journalists visual observations of testing. I suppose H2 damaged steel, could lead to cracks, that when put underwater under tension would cause faster than expected corrosion fatigue like a couple years instead of a couple centuries, they're not totally unrelated. (edited to rephrase corrosion doesn't cause brittleness but brittleness can speed corrosion in the above scheme)

benzofuran 11y ago
Not knowing the particulars of the bridge CP system in place, hydrogen embrittlement is possible but it sounds more like stress corrosion cracking is the major culprit.
- refurb 11y ago
  Where would the hydrogen come from in a situation like this? I know aluminum will produce hydrogen under basic or acid condition, but steel doesn't (I think).
  - Someone 11y ago
    I think from a reaction 2Fe + 3H2O -> Fe2O3 + 3H2 See http://www.madsci.org/posts/archives/2005-12/1134348446.Ch.r.html http://www.madsci.org/posts/archives/2005-12/1134348446.Ch.r...

benzofuran 11y ago

This sounds like a poster child for stress corrosion cracking - which would greatly impact the toughness of the material. Most steels (including stainless) become significantly more brittle under stress when exposed to high chloride environments like seawater while under load - much more than standard fracture mechanics would suggest. Basically there's chloride penetration and then hydrogen generation at the grain boundaries within the metal structure, which significantly reduces the toughness and allows for rapid and catastrophic failure easily.

krschultz 11y ago

Actually that's not 100% correct. Most steel is not at risk, but some forms of high strength steel are susceptible to hydrogen embrittlement in salt water. I don't have enough info to comment on this case, and I don't trust the article because the author can't even get stress vs strain right, but it could be the problem here.

jacquesm 11y ago

Galvanic corrosion can cause steel to become brittle. http://en.wikipedia.org/wiki/Hydrogen_embrittlement http://en.wikipedia.org/wiki/Hydrogen_embrittlement