From: Paul Farber (farber@f-tech.net)
Date: Wed Sep 29 2004 - 18:19:19 PDT
everette wrote:
>Mr. Fareber wrote
>
>"""""
>I don't want to be rude, but when and where has a failure of springs been
>caused by media blasting? I did 6 sets of springs with al. oxide and had to
>cut some serious scale. Never a problem.
>
>I would like to know of real world failure of metal (on our scale... MVs)
>caused by media cleaning or hydrogen emrittlelment.
>
>By reading this discussion, all my MVs should shatter into pieces when I hit
>a bump due to cleaning with media and rust prevention with phosphoric acid.
>
>Pls. provide proof (and not some lab experiment or some yahoo eating 2/3rd
>the way through metal with abrasives) that these things are actual concerns.
>
>Or is this list full of old wives and their old wives tales """
>
>Hydrogen emrittlelment.is a scientific fact, no discussion necesssary-- it
>just happens.
>
> I once put a throttle spring into dilute Hydrocholoric acid --. left for
>1/2 hour or less, spring was clean, rinsed it off and painted with primer
>paint. Spring had been taken off when carburator was removed, and dropped
>in acid to clean oil and grease off it. When stretched to reinstall, it
>broke as soon as it was pulled on.
>
>I had an accident in 3/4 ton 4WD pickup that from factory had single leaf
>front springs, accident caused one spring to bend. The company I was
>working for at the time was big enough that they were self insured. There
>was a complete inspection of truck before repairs were authorized. The
>fellow who did inspection made specific instructions for repair of truck, he
>specificaly said that replacement spring must be new from GMC, not from
>salvage yard, and could NOT be media blasted, acid or caustic dipped. He
>further said old sping must be torch-cut into three pieces.
>
>And to address scale on metal - this is not something that falls out of air
>and attaches to metal. Scale -rust- is metal that has been disolved by
>chemicals in the surrounding air, or something that has gotten on metal
>some other way; and this caused chemical structure change that creates
>scale; hence if you take scale off, aside from embrittlement the remaining
>metal is thinner than before scale showed up. I am reasonably sure that
>springs are over-built and minor rust damage is acceptable. But there is no
>doubt that anything done to them will affect performance.
>
>Embrittlement can be compared to the effect on metal by prolonged hammering,
>much like swords were made by hammering a thick piece of steel until metal
>lost much of the impurities that were in it when made before steel makers
>learned how to make steel without so many impurities. There is a name which
>escapes me for shotgun barrels made by hammnering thin strips of steel
>together around a madrel until desired design of barrel is arrived at,
>another example of metal structure being changed
>by mechical means.
>
>I do not mind being considered an 'OLD WIFE" or even tale of old wife, I
>had much rather err on side of caution than to consider myself smarter than
>people who have the responsibitly of metalurgy design.
>
>
>Sorry to have made such a long post but I have been involved in the
>manufacture of chemical cleaning products both acid and base for several
>years.
>
>Everette
>
>
>
>
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>
>
Wouldn't it be more proper to put your thin carb spring in phosphoric
acid, or even muric acid (which is diluded hydrocloric acid) but not
into full strength metal and flesh eating hydrocloric acid? Spring
break for tons of reason.. this anticodtal tale does not score lots of
points.
The truck spring breaking has not bearing on anything, unless you left
something out?
Yes, if you remoce scale the metal will be thinner... you removed some
of it by removing the scale and also the acid that 'makes' rust will
simply eat it away. Again, unless you forgot to add somthing ?
Parts are not designed with 'extra metal' to overcome corrosion. Things
like paint and metal prep do that. If airplanes had to have 'extra
metal' to overcome corrosion (without any benifits from primers/paints)
they would not be able to fly.
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