X-Message-Number: 4894 Date: Wed, 20 Sep 1995 22:58:05 -0700 (PDT) From: Doug Skrecky <> Subject: time machine construction TIME MACHINE CONSTRUCTION By Doug Skrecky (From April 1992 Canadian Cryonics News) A key requirement for long term storage of human remains is a secure container to insure that nothing goes amiss in the deceased's long journey to the future. Such a "time machine" would require a construction material that is impervious to both air and moisture, is resistent to mechanical stress and does not corrode. Plastics fail on the first count, borrosilicate glass and ceramics are brittle and so fail on the second count, and finally most but not all metals fail by corrosion due to ground water. For example aluminum and lead are dissolved in acid or alkaline solutions, copper and nickel are attacked by sulfides while steel simply rusts in aerated water. The only easily available metals which do not readily corrode are stainless steels, nickel alloys and titanium. Stainless steels derive their corrosion resistance primarily from the incorporation of chromium, molybdenum and nitrogen. *1 Nickel is added to stainless steels in order to eliminate brittleness. *2 The primary vulnerability of stainless is to the chloride ion. In low chloride waters even inexpensive 18% chromium (type 304) steels average corrosion rates of less than 0.000025 millimeters per year. *3 At this rate it would take about 40,000 years to penetrate just 1 millimeter into the metal. Unfortunately this situation changes dramatically when stainless is buried at sites close to the seashore as after just 4 years of burial type 304 plates were virtually perforated. *4 Chromium alone is not enough to ensure that stainless steels will not corrode. Molybdenum and nitrogen must also be incorporated to achieve that. For instance outdoor atmospheric exposure of stainless steels for 32 years at a rural test site yielded no evidence of corrosion. However when these same metals were tested at a sea shore beach front test site great differences were observed. Type 304 with no molybdenum rusted more than type 316 with 2% molybdenum, while type 216 with 2% molybdenum and 0.33% nitrogen remained inert. *5 Recent research has reduced the effective price of stainless steels by increasing their yield strength so that less metal is required. The most widely used high strength stainless alloy is duplex 2205, which contains 22% chromium, 3% molybdenum and 0.2% nitrogen. This alloy is roughly equal to type 216 in general corrosion resistance. *6 Further addition of another 3% chromium plus 2% copper results in a newer alloy called duplex 255, which is able to remain inert even in seawater, while yet being only slightly more expensive than type 316 stainless. *7 A bargain, indeed. What about nickel alloys and titanium? Some bacteria have the nasty habit of attacking metal surfaces and this has produced some unexpected structural failures. When tested with bacteria type 316L was found to be quite resistant and corroded even less than the extremely expensive nickel base alloy Inconel 625. *8 However the situation is quite different with titanium as no cases of corrosion from ambient temperature seawater have ever been reported with this metal. The only known failures involve hydrogen induced embrittlement when titanium was joined to another corroding metal. *9 A titanium casket would thus have to be constructed solely of that metal. Suitable materials for time machine construction are limited at present to titanium and some of the more highly alloyed stainless steels. By using these materials in conjunction with permafrost burial there is a substantial probability that the body of the deceased will eventually attain to a posthumous fame thousands of years from now which would dwarf all others. *1 "Effects of Alloy Composition and Microstructure on the Passivity of Stainless Steels" 376-389 Vol.42 No.7 1986 Corrosion *2 "Nickel Steels in Arctic Service" 46-49 October 1987 Materials Performance *3 "Long Term Corrosion Tests in Rondout Reservoir, New York" 27-33 May 1978 Materials Performance *4 "The Galvanic Coupling of Some Stainless Steeks to Copper - Underground" 16-20 October 1975 Materials Performance *5 "Appearance and Corrosion of Stainless Steels in the Atmosphere" 47-54 February 1988 Materials Performance *6 "Practical Guide to Using Duplex Stainless Steel" 57-62 January 1990 Materials Performance *7 "Duplex Alloy 255 in Marine Applications" 63-67 October 1990 Materials Performance *8 "Ranking Alloys for Susceptibility to MIC - A Preliminary Report on High-MO Alloys" 55-57 January 1991 Materials Performance *9 "Use of Titanium in Petroleum Refining" 48-52 September 1990 Materials Performance Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4894