From: everette (194cbteng@bellsouth.net)
Date: Wed Sep 29 2004 - 16:08:42 PDT
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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