Gun-powder like smell??

[Carburize]

This was posted on the ASM International Web Page

http://www.asm-intl.org

under the general discussion topics of the Ask ASM section - like the author I am intrigued by the statement about being able to "smell" fatigue

Gunpowder-like Smell [Reply]
Yesterday (7/25/04), in my local newspaper there was an article on the deterioration of highway Interstate 5 on the West Coast. The article, titled "The book on I-5: old, tired and in need of repairs," by Dan Weikel of the Los Angeles Times, began with the following paragraph: "Examining the girders that hold up Fords Bridge on the Umpqua River in southwest Oregon, state inspectors noticed a gunpowder-like smell--a tell-tale sign of metal fatigue. Then they saw stress cracks that ran like veins through the main supports." I am a Metallurgical Engineer with some 34 years of professional experience, but I am totally ignorant as to the association of a "gunpowder-like smell" with metal fatigue. Can someone explain and give background for this statement?

 

[Rich2001]

Though I have never seen this on exposed bridge griders, because non-aerobic conditions, but some Microbiological Influenced Corrossion will exhibit a sulfur-type or H2S smell as by-products of the micro-organisms life-cycle.

Here is the link the articles -

http://news.statesmanjournal.com/article.cfm?i=83919

http://www.trivalleyherald.com/Stories/0,1413,86~10669~2293788,00.html

 

[metengr]

Carburize;
I would agree with your 2nd to last statement. The only thing I could think of is that the primer used on the bridge girders emits some type of fume upon exposure to air when the paint cracks OR one of the bridge inspectors went hunting the day before?

 

[mcguire]

Let me offer another hypothesis. Fatigue cracks propagate though weak zones, exposing sulfide inclusions, which can react on this exposure to moist air and give off the sulphrous small of gunpowder.