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From: PAPAI@kcgl1.eng.ohio-state.edu (Jonathan Papai)
Newsgroups: alt.folklore.urban,sci.materials,sci.skeptic
Subject: Re: Delhi Pillar
Date: 9 Feb 1994 21:19:03 GMT

In Message-ID: <CKx1Gp.E4q@ryn.mro.dec.com> On or about Tue, 8 Feb 1994 17:17:09 GMT pierson@msd26.enet.dec.com (dave pierson) posted: >
> India is a big country. PARTS are damp/wet rain foresty. PARTS are Dry.
> Someone who knows can say which is more true of Delhi.

_Nature_ Sep. 12, 1953, vol 172 # 4376, p. 499-500, J. C. Hudson says:

4 by 2 inch specimens of steel and zinc were exposed in air near the pillar and at several other locations. Steel was 1/8 in thick and zinc 1/20 inch thick.

Table 1

Exposure Station         Corrosion Rate mils (0.001 in) per year
                                steel           zinc
Delhi 1950-1951                 0.23            -
Delhi 1951-1952                 0.17            0.006
Goldalming 51-52                1.7             0.042
Sheffield  51-52                4.2             0.51
Khartoum  9 yr. avg.            0.1             0.02
Basrah    8 yr. avg.            0.6             0.04
Singapore 10 yr. avg            0.6             0.04

Hudson attributes corrosion resistance at Delhi to the environment and lists some meteorological data for same:

Table 2

New Delhi Meteorological Observations, 1951

jan feb mar apr may jun jul aug sep oct nov dec Relative
Humidity 74 52 53 42 35 41 63 74 63 50 50 69 0830 h

Relative
Humidity 46 24 33 21 21 26 48 60 52 37 42 47 1730 h

Rain 0.9 0.0 2.1 0.9 0.1 0.5 4.8 3.1 4.1 0.3 0.6 nil (inches)
...

Hudson says below 70 percent RH one can expect little corrosion, while Metals Handbook ninth ed. vol 13, p. 511, ISBN 0-87170-007-7 fig. 2 shows that corrosion rate is negligible below 60 % RH and then increases rapidly, while fig. 1 shows that it increases rapidly above 30 % RH with presence of 0.01 % SO2, for steels.

In any case, for most of the 1500 years the pillar has been there, the SO2 has been low in Delhi. The humidity is also quite low. If the pillar were in Talladega Alabama, where humidity is high, or Cleveland, where SO2 is high, it would be a pile of iron ore by now.

If it were on the beach (exposed to salt spray from the ocean) at Fort Lauderdale it would be gone in very short order.

Jon "long answers to short questions" Papai --
"Lithium has sometimes been used as an alloying element for aluminum; but, on account of the difficulties involved in its use and on consideration of the negligible improvement which it makes in aluminum alloys, no wide application of aluminum-lithium alloys is to be expected." Lucio Mondolfo, 1943