PRODUCTION rereH^rrref-re^mi jyiQlTBDENUAT CpAtltiCR
DIFFUSION LAYEE
BASE. METAL (316 Stainless Steel)
I Vitro's n e w m o l y b d e n u m coating process gives a bright, dense, well b o n d e d coating with a well defined diffusion layer, the company says. This cross-sectional micrograph shows t h e coating, base m e t a l , and diffusion layer
Coating Technique Gets a Boost N e w process uses electrophoretic d e p o s i t i o n , gives a h a r d , bright m o l y b d e n u m coating
.ELECTROPHORETIC
DEPOSITION
as
a
coating technique has been kicking around for a n u m b e r of years. But its use h a s been pretty limited—chiefly to coatings that are subjected to little or no stress. W i t h Vitro Laboratories' molybdenum coating process, though, t h e technique m a y soon become m o r e popular. Vitro h a s used t h e process, which it developed under a n A E C contract, t o coat such materials as stainless steel, Inconel, and Croloy with m o l y b d e n u m 1 to 10 mils thick. T h e coatings show excellent resistance to t h e r m a l cycling and thermal shock, says Vitro, and are impervious enough to protect the b a s e metal against attack b y molten salts and molten metals. Vitro's process has four main steps: preparing a dispersion, electrophoretic deposition, densiflcation, and sintering. T h e heart of t h e process—electrophoretic deposition from n o n a q u e o u s media—differs from other coating t e c h niques such as electroplating o r electro48
C&EN
DEC. 2,
195 7
deposition from a q u e o u s media. Vitro cites these differences: • High ptating voltages without gas evolution at the electrodes. This gives uniform, adherent coatings with high density. • High throwing power. Thickness can b e controlled to ztO.l mil. • Rapid, economical deposition. A large amount of material deposits with an extremely small passage of current; current densities range from 0.05 to 0.03 amp. p e r sq. ft., give deposits up to 10 grams p e r coulomb. Coatings 2 to 4 mils thick build up in 2 0 t o 40 seconds. • Either M e t a l or M i x . T h e first step in the process is t o disperse finely divided metallic particles in a nona q u e o u s solvent. Ball mills, roll mills, or high-speed stirrers reduce the size r a n g e of t h e metallic particles—either molybdenum metal alone o r mixed with varying amounts of t h e oxide. If t h e oxide is used, Vitro says, you need a
reduction step to reduce t h e oxide t o the metal. For a solvent, Vitro uses alcohols such as isopropyl alcohol or nitroalkanes such as nitropropane. The dispersion contains additives to increase t h e activity of the mixture a n d improve its stability a n d shelf life. T h e article to be coated is m a d e one of t h e electrodes a n d hangs in t h e dispersion. T h e deposition process, which is normally pretty fast, is controlled b y electrode spacing, voltage, dispersion concentration, and additives, Vitro says. T h e resulting deposits, though, are not in themselves structural elements. T h e particles must b e sintered together and b o n d e d t o t h e base metal to give a continuous coating. If oxide is used, the reduction step comes in here after deposition. Following this step, the coating is treated to increase its density. Proper particle size distribution is important here, since it helps to g e t the maximum density. A lot of mechanical working techniques can b e used in this step, b u t Vitro has found that hydrostatic pressing at 50,000 to 100,000 p.s.i. is t h e most efficient. Actually, this step can come before or after t h e final sintering. It depends on the size, shape, a n d intended use of the coated article. • Coating Is Sintered, T h e article is sintered in a reducing atmosphere at about 1200° C . - a relatively low temperature compared with the melting point of molybdenum. T h e final result: a bright, dense, well b o n d e d coating with a well defined diffusion layer, according to Vitro. Besides metals, ceramics can also b e coated with molybdenum. I n this case, small amounts of graphite, stannous fluoride, or osmium oxide are added to the ceramic so that it will conduct electricity. This increases conductivity to a point w h e r e a coating will build u p . T h e graphite, o r other material used, is b u r n e d off when t h e coating is fired. Bonding the deposit t o t h e surface is a little more difficult, Vitro says, a n d is directly related to t h e porosity of t h e ceramic itself. Vitro sees the technique as a n e w approach for developing a wide variety of composite materials based on metals, alloys, cermets, and ceramics. Some of the areas, the company says, which show t h e greatest promise: lubricating coatings such as lead monoxide in silver, erosion- a n d corrosion-resistant coatings, ceramic glaze coatings, and special ceramic coatings such as b a r i u m titanate bonded t o a metal base.
In research, in pilot plants . . .
Controlled Volume mitiiPumps for precision metering of minute quantities
T
Seamless Pipe by Extrusion
Curtiss-Wright's metals processing division now makes commercial quantities of extruded steel pipe. Seamless pipes—up to 60 ft. long a n d 20 in. in d i a m e t e r are produced. The trick is a giant extrusion press (above) which has a 12,000ton capacity and measures 126 ft. long, 2 2 ft. wide, a n d 20 ft. high. The extrusion process improves t h e metal's mechanical properties. It gives t h e metal higher strength, higher transverse properties, and more uniform flow patterns, claims Curtiss-Wright. And all modern metals can be processed with this press, company spokesmen add. These include the latest stainless steels, chrome-molybdenum steel alloys, and titanium. Pipes so made can meet many pressure needs found in the nuclear, chemical processing, and oil refining fields.
Standards for CPI Several money-saving standards for the chemical industry are moving closer to reality, reports the Chemical Industry Advisory Board. Here is where several projects of interest to the chemical industry now stand: • Stainless steel analysis. T h e chemical industry has demanded a large number of special variations of AISI Types 316 and 317 stainless steels to fit its needs. AISI has worked out an austenitic stainless designed to meet most of these special cases. CIAB plans t o recommend to t h e CPI that it use the new analysis; if accepted, the analysis will get an AISI designation. • Centrifugal pump standards. ASA Sectional Committee B-73 (C&EN, Dec. 17, 1956, page 6232) has resolved most of its problems and is now preparing Draft Standards. These will be complete b y February 1958 and will
he circulated to pump makers and users. This committee, starting with many thousands of different styles, sizes, and capacities of pumps, has settled on eight sizes to cover t h e c a pacity r a n g e of 5 to 1000 gal. per min. • Nickel conservation. CIAB, AISI, and International Nickel have continued their program of testing the 2O0 series of low-nickel manganese steels as replacements for the high-nickel 3O0 series. Results already in are encouraging—in many cases, the 200 series works, thus halving the amount of nickel needed. This p r o g r a m is scheduled for completion by March 1958. "- Cooling tower standards. ASA Sectional Committee B-76 has divided its work into eight sections and is setting u p subcommittees now. I t may complete its efforts within three years. C I A B met in San Francisco in conjunction with the 8th National Conference on Standards sponsored by American Standards Association. n
miniPump meters clear liquids in quantities within t h e range of 3 milliliters p e r hour t o 3200 milliliters per hour, against pressures to 1O00 psi. Like all Milton FfcoyControlled Volume Pumps, miniPumps are of the reciprocating, p o s i t i v e d i s placement plunger type. They can be operated with a variety of m a n u a l and automatic controls. Available i n Simplex, Duplex and M ultiplex models.
Consfamefric® miniPump delivers straight Urn flow. This is t h e pump t o use where you need continuous, straight-line flow. Use it, for example, in microstmdies involving mixing or nlending of fluids in small-diameter tubing. Capacity, ranging t o 3500 milliliters per hoiar, is adjustable by speed regulation. Write for specifications a n d d a t a o n your a p p l i c a t i o n . Milton Floy Company, Manufacturing Engineers, 1300 E a s t Mermaid Lane, Philadelphia 18, Pa.
CO NTROLUp; VOLUME RUMPS
Engineering Representatives in the United States, Canada, M e x i c o , Europe, Asia, South America and Africa.
D E C . 2,
I957 C & E N
49
[
PEasticizer Data
1
PRODUCTION
TO HELP YOU CHOOSE THE RIGHT
Briefs • » .
PLASTICiZER
this Harf/ex* Plasticizer is non-toxic
Dibutyl Sebacate FDA Accepted • Odorless • Tasteless • Excellent Low Temperature Characterisfics Appearance Color, APHA Odor Specific Gravity, 2 0 / 2 0 ° C Free acidity, as acetic acid Ester Content
Clear liquid 2 5 max. Neutral 0 . 9 3 6 ± 0.003 0 . 0 1 % max. 9 9 . 0 % min. Other Uses
Vinyl chloride r e s i n s , c o p o l y m e r s and plastisols, safety glass a n d safety plastic interlayers, cellulose a c e t o b u t y r a t e , neop r e n e a n d acrylonitrile-butadiene copolymer l o w t e m p e r a t u r e formulations, r u b b e r h y d r o c h l o r i d e films. Dicapryl Phthalate-least expensive of the phthalate plasticizers—is FDA accepted for foods of high water content only. H A R C H E M also p r o d u c e s a full line of sebacate, p h t h a l a t e , adipate a n d polymeric plasticizers. T h e H a r c h e m Division laboratories will gladly assist y o u with y o u r plasticizer problems, o r will supply additional data including f o r m u lation test r e s u l t s a n d f o r m u l a t i o n suggestions for a n y Harflex Plasticizer. A d d r e s s inquiries to Dept. H-39. Z ~ THE KEY TO
HARCHEM
W*®
BETTER PLASTICS
HARCHEM DIVISION WAL_L_ACE & T I E R N A N , I N C . ZS M A I N S T R E E T . B E L L E V I L L E 9 . N E W J E R S E Y IN CANADA: W. C. HARDESTY CO. OF CANADA. LTD.. TORONTO
TRICHLOROMELAMINE (89%
available
chlorine
min.)
A n effective y e t s t a b l e g e r m i c i d e • Highest stable chlorine content # Sterilizes i n presence of high organic c o n t a m i n a t i o n • Sterilizes a t high t e m p e r a t u r e s • H a s g o o d s h e l f life • C o m p o u n d s easily Data and samples available, write for bulletin PX-2
W A L L A C E 8c T I E R N A N I N C O R P O R A T E D 2 5
50
C &EN
MAIM STREET. BELLEVILLE
D E C . 2,
195 7
^. N E W
JERSEY
• Standards for disposal of radioactive wastes need t o be revised, say Paul C. Tompkins and Myron B . Hawkins of N a v a l Radiological Defense Laboratory i n Sam Francisco. Present standards were developed for M a n h a t t a n project, are now o u t of date, they say. Power reactors, weapons testing, isotope a p plications, a n d reprocessing plants all add t o the amount of radioactive matter entering t h e environment. • Atlantic Research h a s licensed its new heterogeneous liquid monopropellant, Arcogel, to Thompson Products. The license includes t h e right to purchase, use, a n d sell t h e gel propellant. • The Navy h a s been testing t h e performance of an antisubmarine patrol blimp with a skin of coated Dacron. DurLngfour months of trial flights, t h e Navy found that helium loss was cut in half. The envelope is m a d e u p of t w o layers of Dacron fabric combined with an inside coating of neoprene, a binding layer of neoprene, and an outside coating of aluminized Hypalon synthetic rubber, Weight of t h e laminated clothi: 15 V 2 ounces p e r sq. y d . M a r c o - W o o l d r i d g e h a s established a computation consulting a n d service bureau.. T h e bureau will be operated as a pa_rt of the company's digital computing center. T h e company plans a consulting service in computer applications a n d digital computing services including numerical analysis, programming, and equipment rental. • Flcjorulon L a b o r a t o r i e s h a s created an engineering and design department to give c u s t o m service to those who are usirLg or might want t o use the plastics of t h e fluorocarbon family. Fluorulon will experiment with n e w uses of TefLon, K e l - F , Genetron, Fluorethylene, and Polyfluoron. • Normally
poor
adhesive
bonding
properties of polyethylene can b e improved by treating t h e plastic with chromic acid, according t o Army Ordnantce. T h e Army's tests showed that treating with concentrated chromic acid chemically alters the surface of polyethylene so t h a t good peel- a n d shearstrength bonds are possible. T h e Army recommends t h e treatment prior to bonding whenever high-strength bonds are necessary, according t o a Department of Commerce report.
