Clean Steel Surfaces Research Articles

Thin film testing of biodiesel degradation residues and their solubility

With broader application of biodiesel, reports about residues, varnish and other solid deposits in engines emerge more frequently. A thin film degradation test, originally developed for lubricant studies, was employed to investigate fuel vaporization, acid buildup and solubility of degradation products. Films of 25, 100 and 500 μm thickness of rapeseed and palm fatty acid methyl esters (FAME) as well as hexadecane were exposed to 50 °C and 90 °C for up to 3000 h in dry or humid atmosphere on steel surface. Hexadecane produced clean steel surfaces, while FAME films would leave at least 10% residues or more in thicker films. Simple soaking in acetone or tetrahydrofuran dissolved FAME films nearly completely, if degradation was shorter than 1000 h at 90 °C. But in non-polar solvents FAME films became insoluble after much less degradation. As little as 50 h degradation at 50 °C was enough to produce a viscous bottom layer, which would not dissolve in fresh FAME or heptane. Other solvents were tested as well, further showing that FAME degradation products are poorly compatible with fuel-like solvents, such as xylene, heptane or fresh FAME. Formation of immiscible bottom phase may promote buildup of residues, deposits and varnish in fuel systems.

Electrochemical Determination of Hydrogen Entry to HSLA Steel during Pickling

Pickling with hydrochloric acid is a standard method to clean steel surfaces before hot‐dip galvanizing. When normal low strength steels are pickled, hydrogen formed in pickling reactions does not have any significant harmful effect on the mechanical properties of steel. However, in pickling of steels with higher strength, the penetration of hydrogen into the steel may cause severe damages. The effect of pickling of high‐strength low‐alloy (HSLA) steels was investigated using a cell construction based on the Devanathan‐Stachurski method with modified anodic surface treatment and hydrogen production using acid. The penetration and the permeability of hydrogen were measured using an electrochemical cell with hydrochloric acid on the one side of the steel sample and a solution of NaOH on the other side. No protective coating, for example, palladium on the anodic side of the sample, is needed. The penetration rate of hydrogen into the steel and exit rate from the steel were lower for higher strength steel.

Dynamics of cathode spots in low-pressure arc plasma removing oxide layer on steel surfaces

The dynamics of cathode spots has been investigated in low-pressure arc plasma for removing oxide layer on low carbon steel surfaces. The motion of cathode spots was observed with a high speed camera, and the arc voltage was analyzed by fast Fourier transform. The spots move on clean steel surface as a random walk, and the low-frequency components dominated the voltage waveform. However, the spots on steel surfaces with oxide layer tend to burn on the rim of the eroded area formed in the previous arcing, and the low-frequency components decrease correspondingly. The “color” of the colored random noise for arc voltage varies from the approximate brown noise for clean steel surface to pink noise for thick oxide layer, where the edge effect of boundary is considered to play a significant role.

Is pickling rate of A36 steel dependent on the saturation of the pickling bath in acidic sulfate media?

In metal processing, pickling baths containing sulfuric acid used to clean steel surfaces are assumed that are exhausted when the bath becomes saturated with ferrous sulfate at around 80–90g/L. At saturation, the bath is regarded as ineffective and is discarded as waste material. To our knowledge, however, there is no experimental evidence showing that saturation determines the exhaustion of the bath and stops the pickling reaction. We therefore tested whether ferrous sulfate saturation stops the pickling reaction by adding different amounts of ferrous sulfate to a 20% sulfuric acid pickling bath and analyzing the pickling rate of A36 steel. We found that pickling rates were similar in saturated baths containing ferrous sulfate concentrations as high as 300g/L. We have thus confirmed that the pickling rate depends primarily on the proton concentration of the bath.

Influence of Galvanized Coatings on Abrasion Circle Friction Stir Spot Welding Aluminium to Steel for Automotive Applications

It has previously been shown that dissimilar Al-alloy and un-coated steel automotive sheets can be successfully welded with a cycle time of less < 1 s using a novel solid state joining approach; Abrasion Circle Friction Stir Spot Welding (ABC-FSSW). The ABC-FSSW technique provides an effective strategy for exposing a larger clean steel surface during welding than conventional FSSW, allowing high failure energy joints to be produced. In this study the influence of different steel zinc coatings on the viability of the ABC-FSSW process has been systematically investigated - focusing on the effect on the process window, weld temperatures, and joint performance. The effect of a galvanised coating on the weld formation, zinc dispersal in the joint, and interface intermetallic reaction behaviour are discussed.

Diode laser beam absorption in laser transformation hardening of low alloy steel

Defining and controlling the absorption of the laser beam is important since all of the heating energy is brought to the material through absorption. Even small variations in the absorption change the laser power needed by hundreds of W. In this study the absorption of a diode laser beam to low alloy steel has been measured by a liquid calorimeter and the surface temperature has been measured with a dual wavelength pyrometer. The varied processing parameters were the power intensity of the beam, the interaction time, and the angle between the surface and the optical axis of the laser beam. Surface temperatures during hardening varied from the Ac1 temperature to the melting point. Tests were done with a 3 kW diode laser with a 12×5 mm hardening optic. The absorptivity of a machined clean steel surface ranged from 46% to 72% depending on the processing parameters. Aluminum oxide blasting of the surface increased the relative amount of energy absorbed to the work piece. The coupling rates for blasted surfaces varied from 66% to 81%. Best absorptivity was achieved by applying graphite coating on the surface. Absorptivity values in excess of 85% were measured.

Interfaces between Natural Rubber and Metals. Part I. A Study of the Interaction between Squalene and Steel Using XPS and SIMS

Abstract 1. XPS and SIMS in conjunction with a suitably chosen liquid model system form a powerful and highly complementary set of analytical tools for the study of the interaction between steel surfaces and unsaturated molecules; 2. We have presented evidence for an oxidative mechanism for the formation of a chemical bond between freshly abraded steel surfaces and squalene at 160°C. Such a bond can only be formed by unsaturated molecules on clean steel surfaces which exhibit a catalytic activity for the oxidation reaction. 3. This squalene approach appears to be very useful for the study and optimization of the bonding of 1,4-dienes to steel directly. The effects of the individual compounding ingredients on the rate of bond formation might conveniently be studied in this way in order to optimize compound formulations and surface preparations. The usefulness and limitations of a liquid model system such as squalene for the study of various aspects of natural rubber chemistry have been documented.

Phosphoric acid treatments for steel. I. The nature of coatings produced by the action of phosphoric acid on steel

AbstractThe nature of the mixed phosphates present in coatings produced by the action of phosphoric acid on a clean steel surface has been investigated. It has been shown that the coating composition changes with time of exposure to atmospheric oxygen. The role of oxygen in the reaction mechanism is discussed.

Protective films for pilot‐plant deodorizers

SummaryWith mild agitation, soybean oil is not appreciably contaminated by contact with clean steel surfaces unless the fatty acid content is above 0.1% and the temperature above 150°C.It has been shown that an oxidized oil film is an effective coating for metals used in the construction of pilot‐plant deodorizers. Such a film, to be most effective, should be washed free of unoxidized, noncoherent oil with a suitable solvent. If the metal is properly coated an oxidation‐stable and flavor‐stable oil can be obtained from the deodorizer, providing the oil has been properly refined and bleached. The oil film is nearly the equivalent of a glass surface in its effect on oil stability, is easily formed on a metallic surface, and can be readily removed when the metal is cleaned with caustic.A silicone varnish film baked on the metal surface is somewhat less effective than an oil film. Other methods of treating steel or stainless steel, which include coating the metal with a polymeric ether‐linked wax, grit‐polishing, and electropolishing, are fairly effective in reducing corrosion of the metal during deodorization.

Effect of Temperature on Lubricant Films

THE friction apparatus developed by Bowden and Leben1,2 has shown that when clean steel surfaces slide on one another, the motion is not smooth but proceeds in a series of irregular jerks. This apparatus has also been used for comparing the lubricating properties of various substances. With the high loads and low speeds employed, the conditions which obtain correspond to boundary lubrication. Experiments show that when a non-polar lubricant such as medicinal paraffin oil is used, the motion still proceeds in stick-slips, though the average value of the friction is lower than for the dry surfaces. Certain long-chain fatty acids and small quantities of these acids in a non-polar oil will, however, cause continuous sliding1,3. This property has been used to detect the oxidation of non-polar oils on heating. The original oil gives a jerky motion; when a certain amount of oxidation has occurred the motion becomes smooth. The rate of this oxidation becomes appreciable with most oils at temperatures above 150° C. and the change in the frictional behaviour is irreversible on subsequent cooling3.