Electropolished Stainless Steel Research Articles

First results of RASMUS: Source gases in the mesosphere

We present the first results of project RASMUS ( R ocket-borne A ir S ampler for the M esosphere and U pper S tratosphere). Besides N 2O and CH 4, H 2, CO and CO 2, stable halogenated hydrocarbons such as CF 4, CHClF 2, CClF 2-CF 3 and CF 3-CF 3 have been measured for the first time at about 60 km altitude. RASMUS is a new LHe-cooled cryogenic whole-air sampler which allows collection of 4 samples of about 4 ℓ STP at freely programmable height levels between 65 and 40 km. The samples are collected at the apogee and during the descent phase, at subsonic velocity of the instrument. They are frozen out on gold plated cold fingers suspended in electropolished stainless steel containers with liftable sampler caps. After parachute-recovery they are analyzed using GC and GC-MS techniques. Results of the first RASMUS flight on May 6, 1987 from ESRANGE/Sweden are presented and discussed in the light of model predictions.

Phosphorus implantation of 304L stainless steel

Electropolished 304L stainless steel specimens were implanted near room temperature with 175 keV phosphorus ions to fluences from 4.0 × 10 17 to 4.0 × 10 17 P + cm −2. Microstructural characterization of the samples with an analytical electron microscope revealed an f.c.c.-b.c.c. transformation at fluences near 1.0 × 10 17 P + cm −2, followed by amorphous phase formation at 3.5 × 10 17 P + cm −2. Precipitation of a hexagonal phase, indexed as Fe 2P, from the amorphous matrix occurred at fluences of 3.75 × 10 17 P + cm −2. Anodic polarization measurements performed on specimens implanted to 3.5 × 10 17 P + cm −2 to generate an amorphous phase showed no significant decrease in the critical anodic current density as compared with that in unimplanted 304L stainless on implanted specimens, whereas unimplanted specimens showed extensive pitting attack.

Trace gas emissions from a mid‐latitude prescribed chaparral fire

Gas samples were collected in smoke plumes over the San Dimas Experimental Forest during a 400‐acre prescribed chaparral fire on December 12, 1986. A helicopter was used to collect gas samples over areas of vigorous flaming combustion and over areas of mixed stages (vigorous/transitional/smoldering) of combustion. Sampling was conducted at altitudes as low as 35 m and as high as 670 m above ground level. The samples, collected in 20‐L Tedlar bags, were returned by helicopter to our field laboratory and immediately transferred to electropolished stainless steel canisters. Analyses for the trace gases carbon dioxide (CO2), carbon monoxide (CO), hydrogen (H2), methane (CH4), total nonmethane hydrocarbons (TNMHC), and nitrous oxide (N2O) were performed within hours after collection. Samples of gas were also collected upwind of the burn and analyzed to determine ambient background levels. Mean emission ratios (ΔX/ΔCO2, where X is equal to each species, vol/vol) determined for these gases relative to CO2 were generally lower (except for N2O) than mean emission ratios previously reported for large biomass‐burning field experiments. No substantial differences in CO2 normalized emission ratios for these gases (except for N2O) were determined when samples from vigorously flaming and mixed stages of combustion were compared. Emissions from flaming portions of chaparral, however, would be expected to release disporportionately larger volumes of trace gases into the sampled smoke plumes. This, coupled with the very high surface‐to‐volume fuel ratio typical of a chaparral fire (which minimizes the smoldering stage), may have accounted for the consistency in the emission ratios.

Comparison of solid adsorbent and stainless steel canister sampling for very low ppt-concentrations of aromatic compounds (≥C6) in ambient air from remote areas

The applicability of stainless steel canister and solid adsorbent sampling has been studied for very low concentrations (> 15 ppt) of compounds ≥ C6 in ambient air samples from remote areas (Arctic). Different cleaning methods were tested to get sufficiently low blank values for the solid adsorbents Tenax TA and Carbotrap for benzene and toluene. Two techniques are described based on high-vacuum or hot air pretreatment which lowered the blank to less than 1 ppt (sampling volume 10 and 60 l, respectively). Sufficiently low blanks could be maintained for a storage period of at least 1 week. However, this required a careful selection of suitable sealing and tube materials. Furthermore, the long-term stability of samples collected with electropolished stainless steel bottles was tested. No losses were observed for benzene and toluene during 1 month storage. Quantitative analysis was carried out by combining thermodesorption or cryogenic enrichment with high resolution gas chromatography. Both sampling techniques are suitable for very low ppt-concentrations of benzene and toluene but their application range is complementary (e.g. grab sampling versus sampling over longer periods). A detailed description of all working procedures and methods is given including blanks and reproducibility data.

Colouring of PPS

Electropolishing is a surface finishing process of metals and alloys that enhances brilliant surface finishes with low surface roughness values. The most widely used electrolytes for the electropolishing of stainless steel are varying concentrations of phosphoric and sulphuric acid, and occasionally additives such as chromic acid. The objective of this study was to assess the performance of three commonly used industrial electrolytes in terms of the surface gloss of electro polished stainless steel AISI 316L. Each electrolyte had varying sulphuric-phosphoric acid combinations with or without chromic acid. The following electropolishing conditions were assessed: current density, bath temperature, electropolishing time, electrode position, and initial surface texture. The results revealed that adding chromic acid to the electrolyte did not significantly enhance gloss ranges. Current density and electropolishing time were the most significant parameters of surface gloss.

Alpha spectrum evaluation method for the simultaneous determination of plutonium, americium and curium

A method based on the geometric progression decrease of the counts in the far tail of the alpha spectrum is described for the simultaneous determination of plutonium, americium and curium by alpha spectrometry. For evaluating the precision and accuracy, synthetic mixtures were prepared from solutions of enriched isotopes and sources were prepared by direct evaporation method using tetraethylene glycol /TEG/ as a spreading agent and electropolished stainless steel discs as the backing material. Precision and accuracy of about 1% is demonstrated in the determination of244Cm/239Pu,241Am/239Pu,244Cm/233U,241Am/233U and239Pu/233U alpha activity ratios using a 450 mm2 silicon surface barrier detector.

Effect of container preparation on the growth of protium and methane impurities into tritium gas

Ten vessels, candidates for the unperturbed storage of analytical calibration gases containing tritium, were investigated. Contamination of 99.7% tritium gas at STP by each container over one year was a function of vessel material and surface preparation. Cylinders of aluminum and stainless steel (SS) could restrict protium ingrowth better than could hydroxyl-rich borosilicate glass. Canister surfaces with the least surface area also allowed the least protium and methane ingrowth: slower exchange of hydrogen isotopes between material and gas, and less occlusion of organic contaminants are likely causes. Protium ingrowth from bulk metal was successfully inhibited by the thin surface oxide or deformed near-subsurface structure present on dry-paper polished SS; gold ion plating such a vessel was no more effective in minimizing protium. Methane could be nearly excluded from tritium by careful cleaning of container material. Borosilicate glass and dry-paper polished SS appeared more effectively cleaned by solvent washing than did electropolished SS or burnished aluminum. Electrocleaning or oxygen discharging procedures removed hydrocarbons effectively, but led to high protium injection to metal. Careful handling of treated container parts is important. Three to four monolayers of adsorbed organics on a surface can cause observable protium and methane impurity in tritium gas.

Study of radiation interchange in an enclosure consisting of plane isothermal and adiabatic surfaces

This study examines the validity and accuracy of the commonly used diffuse, specular, and diffuse-specular constant property models for predicting radiant interchange among real surfaces by comparing analytical predictions with experimental data. The materials tested were sandblasted stainless steel, electropolished stainless steel, rough electroplated gold, and smooth electroplated gold. Measurements were made over the temperature range from 310.4 ‡K to 644.0 ‡K. The data indicates that the simple diffuse model yields reasonably accurate radiant heat exchange predictions. The variation in the radiative surface characteristics with direction should be accounted for in some manner, particularly for specular or nearly specularly reflecting surfaces.

An Experimental Examination of the Validity of the Commonly Used Methods of Radiant Heat Transfer Analysis

In this work the validity and accuracy of the commonly used methods of radiant heat transfer prediction were checked experimentally. The local irradiation was measured for five different materials in two simple configurations. The materials tested were sand-blasted stainless steel, electropolished stainless steel, rough electroplated gold, smooth electroplated gold, and PV100 white paint. Measurements were made over the temperature range from 50 deg F to 850 deg F for each of four sets of geometric parameters. The predicted values of local incident fluxes using the diffuse, specular, and diffuse-specular models were compared with experimental data. The data agree with the diffuse model within the accuracy of the measurements for all the surfaces tested. Additional conclusions, recommendations, and procedures, which should be followed for more realistic radiant heat transfer calculations, are given in the body of the paper.

Potentiometric titration of hydrogen peroxide with an electropolished stainless steel electrode

The preparation and use of a stainless steel indicator electrode in the accurate potentiometric titration of aqueous hydrogen peroxide are described. The results agree excellently with those obtained by a standard colorimetric weight-titration procedure. The nature of the titration curves, potential changes and the factors affecting them are discussed. Rapid potentiometric titrations directly to the equivalence-point potential are possible, owing to the nature of the titration curve.