Spray Fog Research Articles

Effect of plasticizer on the thermal, mechanical, and anticorrosion properties of an epoxy primer

The influence of the glass transition temperature and the mechanical and anticorrosion properties of factors such as the amount of plasticizer added to an epoxy primer were investigated by DSC (differential scanning calorimeter), DMA (dynamic mechanical analysis), stress-strain tests, salt fog spray tests, accelerated tests, and electrochemical tests.

CHARACTERIZATION AND MODELING OF A HIGH-PRESSURE WATER-FOGGING SYSTEM FOR GRAIN DUST CONTROL

Grain dust, a health and safety risk, is generated whenever grain is loaded into or unloaded from hoppers andequipment. This research investigated airflow models and evaluated the particle dynamics from a high-pressure water-foggingsystem for potential dust control at a grain-receiving hopper. Experiments were performed in a test chamber, representinga narrow section of a grain-receiving hopper. A 0.2 mm (0.008 in.) spray nozzle was used to produce a plume of fog directedacross a free-falling grain column. More than 90% of the fog droplets ranged from 10 to 40 .m in diameter. Average dropletvelocities in the plume cross-section were over 10 m s-1 at 7.6 cm from the nozzle. The air-velocity pressures at 7.6 cm wereparabolic in the radial direction, with maximum pressures over 275 Pa (1.1 in. H2O). Airflow distributions, grain dusttransport, and spray droplet trajectories within the test chamber were modeled in three dimensions using FLUENT, whichis a computational fluid dynamics (CFD) software program. Induced airflow from the spray fog caused recirculation of theair and dust particles in the lower part of the chamber. This recirculation pattern transported the dust from the grain pile backinto the spray plume, where it mixed with the spray fog. The spray produced deposits on the surface of the grain pile rangingfrom 0.1 to 0.4 mg cm-2 s-1. However, when the grain pile filled the chamber and was positioned directly in the spray plume,the grain surface deposits were 1.2 mg cm-2 s-1 at the grain peak. The spray produced deposits on the sidewall of the chamber.Sidewall spray deposits were 11 mg cm-2 min-1 in the middle of the test chamber and 1.5 mg cm-2 min-1 near the outlet. Thesidewall dust deposits during spray treatment ranged from 1.2 to 0.5 mg cm-2 min-1 and correlated with the spray depositswith an R2 of 0.95.

Desulfurization of Flue Gas by the Principle of Acid Rain

Desulfurization and purification of flue gas have long been important issues regarding environmental conservation. However, acid rain and atmospheric pollution are still generated by many chimneys all over the world. Since flue gas in general contains much SO2 and water vapor, desulfurization could be realized by condensing SO2 and water as acid water in a process similar to the formation of acid rain. This process was tested using a water fog spray system which includes a cooling tower. Flue gas generated by burning LP gas and added SO2 gas were introduced to the top of the cooling tower. The results showed that as the temperature of the flue gas approached the water temperature, the desulfurization ratio increased and reached nearly 100%. When PVC film was burned to generate gas containing Cl2 and its black smoke compounds, water fogging resulted in a change from black to white smoke generated from the system. It is considered that simple and inexpensive modification of existing chimneys can eliminate the problem of chimneys producing atmospheric pollution and acid rain.

Laser beam welding of Al–Mg–Si–Cu alloy 6013 sheet using silicon rich aluminium filler powders

Butt welds of 1.6 mm thickness sheet of the Al–Mg–Si–Cu alloy 6013 were produced using a 3 kW Nd : YAG (neodymium : yttrium–aluminium–garnet) laser. The sheet was welded in the T4 and T6 temper conditions using filler powders of alloys Al–5%Mg, Al–12%Si, Al–20%Si and Al–40%Si. Microstructure, hardness profile, tensile properties and corrosion behaviour of the welds were investigated in the as welded conditions and after a post-weld heat treatment to the T6 temper. Pores were observed in the fusion zone, which exhibited a dendritic microstructure. Post-weld artificial aging increased the hardness in the fusion zone owing to precipitation of strengthening phases. Joint efficiencies between 80 and 90% were achieved for 6013 alloy welds in the as welded T4 condition. After a post-weld heat treatment to the T6 temper, the strength approached 90% of the ultimate tensile strength of the base material 6013-T6 for welds made with silicon rich filler powders. Joints in the as welded T4 and post-weld heat treated T6 temper conditions suffered pitting when exposed to an intermittent acidified salt spray fog. In the as welded T6 condition, welds exhibited zones adjacent to the fusion boundaries that were not corroded. These corrosion free zones were not observed after alternate immersion tests in 3.5%NaCl solution. As welded 6013-T4 joints were susceptible to stress corrosion cracking in the heat affected zone when immersed in an aqueous chloride–bicarbonate solution.

Influence of Environmental Aging on Properties of Polymeric Mortars

The emergence of polymeric mortars as a class of materials with applications in civil engineering requires a systematic study of their properties, including mechanical strength and durability under severe environmental conditions. This study reports results based on tests of polymeric mortars, both with epoxy and polyester resins, after exposure to (1) immersion both in distilled and in salt water, (2) salt fog spray cycles (8 h of salt fog, followed by 16 h drying, at 35°C), and (3) temperature cycles [12 h at 20 and 50°C, respectively, with relative humidity (RH) kept at 80%]. Additional tests for humidity cycles at fixed temperature and ultraviolet rays are reported elsewhere. Moisture absorption is analyzed based on mass changes for submerged specimens and Fickian type behavior evaluated. Compressive and bending strength degradation, as well as increase of brittleness, are examined for these accelerated actions and preliminary interpretation advanced. The relative severity of the effects is graphically displayed, tabulated, and analyzed. Brittleness increases more rapidly, under salt fog, for epoxy mortar and bending strength reduction at 10,000 h is also higher (50%) for epoxy mortar than for polyester mortar (32%). Thermal cycles also provoked greater deterioration of bending strength on epoxy mortars. Compressive tests led to results of similar tendency, but with smaller differences.

Testing the influence of the plasticizers addition on the anticorrosive properties of an epoxy primer by means of electrochemical techniques

The effect of the plasticizer (butyl benzyl phthalate, BBP) addition on the corrosion resistance properties of paint films has been investigated by means of different electrochemical techniques (EIS and ac/dc/ac) and accelerated tests (salt fog spray). Primers based on epoxy resin were prepared with different plasticizer content (0, 1.5, 3, 5, 11, 16 and 25% in weight ratio to epoxy resin). An optimum quantity of plasticizer content (1.5–3%) was determined that gave the maximum anticorrosive performance of the epoxy primer. Results offered by each one of the techniques were quite similar and the ac/dc/ac one offered the results in a very short time (24 h).

Design, Construction and Testing of a System for Accelerated Simulation of Damage by Atmospheric Corrosion on Electronic Equipment

The corrosion resistance of electronic devices has been tested for many years using some methods like cycle humidity test, field tests and salt spray (fog) test. Nevertheless, none of these test methods show a strong relationship with the real service conditions. For this reason, it is necessary to develop methods and equipment suitable for the accelerated simulation of real atmospheric corrosion phenomena. This article will demonstrate the need to develop a test and the necessary equipment to reproduce the damage in electronic devices with the possibility of using it for a fast evaluation of equipment failure.

Corrosion protection properties of electroless Nickel/PTFE, Phosphate/MoS 2 and Bronze/PTFE coatings applied to improve the wear resistance of carbon steel

The aim of this work is the evaluation of corrosion behaviour of some industrial coatings on carbon steel, utilised to improve tribological behaviour. In particular, composite electroless nickel coatings with polytetrafluoroethylene (PTFE) particles, sintered bronze in PTFE matrix layers and zinc phosphates—with and without MoS 2 coatings—were analysed. Salt spray fog exposure and electrochemical tests were carried out. Electroless nickel coatings showed the best protection properties with a good barrier protection, because of the coating structure: an external layer, which contains PTFE particles improving tribological properties, and an inner nickel layer, which protects against corrosion because of barrier effect. PTFE-coated sintered-bronze samples showed limited corrosion resistance due to the high number of defects present. The application of a MoS 2 polymer-embedded layer improves the characteristics of phosphate conversion coatings, which, by themselves, cannot assure good protection.

Strength reduction in screw fasteners resulting from outdoor exposure

It is well known that corrosion can weaken structures over time, but because corrosion rates can differ significantly from location to location, it is difficult to predict the amount of weakening that can occur for a particular structure used outdoors in a given location. Over the years, salt fog testing has been used to help predict how a structure might degrade over time resulting from exposure. The most common tests are based upon MIL-STD 810 “Environmental Engineering Considerations and Laboratory Tests,” and ASTM B117 “Standard Practice for Operating Salt Spray (Fog) Apparatus.” Although these standards give guidelines on conducting accelerated tests, they provide no insight as to the real world exposure level corresponding to a test condition, i.e. an acceleration factor. Small screw fasteners that had been exposed in service for two years in a marine environment were visually compared to similar fasteners exposed to varying lengths of time up to 22 days, under accelerated weathering conditions as specified in MIL-STD-810, and ASTM B117. A salt fog apparatus was used for the exposure testing. An acceleration factor for this service was determined, and found to be consistent with corrosion rate research conducted for other marine environments. Research of corrosion rates in other marine environments found that they can vary significantly, and are most strongly dependent on temperature, wind speed and direction, and rainfall. Mechanical testing of the screws removed from service was compared to those subjected to the accelerated weathering conditions. Testing was conducted with a servo-hydraulic test machine fitted with custom grips designed to load the screws in their as-installed configuration. Both the screws returned from two years of service, and screws subjected to the salt fog for various amounts of time up to 22 days were tested in this fashion. In addition, standard single lap shear testing was conducted on several screws exposed to the salt fog for various amounts of time up to 22 days. The amount of time for the screw strength to drop below an acceptable level was determined.

Corrosion behaviour of Ti 3Al and Ti 3Al–11 at.% Nb intermetallics

The corrosion behaviour of Ti 3Al and Ti 3Al–11 at.% Nb was studied and compared to Ti with salt fog spray test and electrochemical methods in NaCl, HCl, H 2SO 4 and HNO 3 solutions. The corrosion mechanism of Ti 3Al in salt fog is suggested to be the dissolution of Al and oxidation of Ti. Polarisation curves of Ti 3Al and Ti 3Al–11Nb in 0.5N NaCl and 1.0N HCl solutions showed passive and pitting behaviour. However, Ti 3Al–11Nb showed higher pitting potentials than Ti 3Al, especially in 1.0N HCl solution. Polarisation of Ti, Ti 3Al and Ti 3Al–11Nb in 1.0N H 2SO 4 solution demonstrated passive behaviour. In 1.0N HNO 3 solution, these intermetallics exhibited passive behaviour but without an active region. The addition of 11 at.% Nb to Ti 3Al improves the corrosion and pitting resistance in some acid and neutral chloride solutions. It is believed that the improvement is related to the specific microstructure and composition containing Nb with a high corrosion resistance.

Epoxy-acrylic microgels in electrodeposition coating films

Epoxy-acrylic microgels (EAM) have been prepared via an aqueous dispersion polymerization of a mixture of acrylic monomers in the presence of the cationic soap with the quaternary ammonium salt groups and 2,2′-azobis(2-methylpropionitrile) (AIBN) as an initiator. The prepared microgels have a bimodal particle size distribution of 10 and 52 nm, and consist of a cross-linked acrylic polymer and cationic epoxy resin. Rheological data from the pendulum type rheovibron show that the presence of the spherical microgels in electrodeposition paint perturbs the flow of the surrounding fluid in a low shear field. A scanning electron microscope (SEM) showed that edge protection (%) at a knife blade increased proportionally with the amount of the microgel in the coating formulation. The microgels also provided excellent corrosion resistance; the cured film containing more than 7% microgels was free of rust spots after 168 h of the salt fog spray test. These results lead to the conclusion that EAM has a remarkable ability to perturb the thermal flow during the curing process and can be used in electrodeposition coating formulations to provide edge protection.

Corrosion protection of aluminum alloys by coatings of unique poly(diphenyl amine)-derivative conducting polymers

Results showing exceptional corrosion protection afforded by coatings of unique poly(diphenyl amine)-derivative (P(DPA1)) Conducting Polymers (CPs) to aerospace Al alloys 2024 and 7075 are presented. The CPs were formulated as emulsions in environmentally benign solvents, and could be applied using conventional methods such as spray/dip coating. Anti-corrosion properties were tested comparatively with commercial chromate coatings (Accelagold, Alumigold) using: salt spray fog chamber (vide ASTM B-117-94, US-MIL-C-5541E methods); Cyclic Polarization, Linear Polarization, Tafel scans; immersion/weight loss; scratch tests/scanning electron microscopy; adhesion; thermogravimetric analysis (TGA); paintover. Typical results from the fog chamber tests were (AA 2024): uncoated, 61 pits; Accelagold, 6; Alumigold, 19; P(DPA1), 0. Cyclic polarization scans for P(DPA1)/(AA2024) showed absence of hysterisis loops, identical forward/reverse scan paths. An overall Degree of Corrosion Protection factor combining all test methods indicated corrosion protection for P(DPA 1) coatings 200 X that of uncoated alloy, and much superior to that of poly(aniline)/sulfate as well.

Electrochemical Impedance Spectroscopy Study of the Corrosion Process on Coated Galvanized Steel in a Salt Spray Fog Chamber

Abstract The behavior of three different paint systems was investigated using the electrochemical impedance spectroscopy (EIS) technique. The coatings, based on chlorinated rubber, alkyd resin, and...

Corrosion resistance of single TiN layers, Ti/TiN bilayers and Ti/TiN/Ti/TiN multilayers on iron under a salt fog spray (phohesion) test: an evaluation by XPS

The corrosion resistance of three different TiN coatings on iron (single TiN layer, Ti/TiN bilayer and Ti/TiN/Ti/TiN multilayer) subjected to a salt (ammonium sulphate and sodium chloride) fog spray (Prohesion) test has been investigated by means of x-ray pbotoelectron spectroscopy (XPS). The relative intensities of the Fe 2p and 0 1s signals in the XPS spectra of the corroded samples increase with their extent of degradation. The results show that the corrosion resistance of these coatings decrease in the order bilayer > multilayer > single layer.

Corrosion resistance of single TiN layers, Ti/TiN bilayers and Ti/TiN/Ti/TiN multilayers on iron under a salt fog spray (phohesion) test: an evaluation by XPS

The corrosion resistance of three different TiN coatings on iron (single TiN layer, Ti/TiN bilayer and Ti/TiN/Ti/TiN multilayer) subjected to a salt (ammonium sulphate and sodium chloride) fog spray (Prohesion) test has been investigated by means of x-ray photoelectron spectroscopy (XPS). The relative intensities of the Fe 2p and O 1s signals in the XPS spectra of the corroded samples increase with their extent of degradation. The results show that the corrosion resistance of these coatings decrease in the order bilayer>multilayer>single layer. Copyright © 1999 John Wiley & Sons Ltd.

Plasma nitriding and plasma nitrocarburizing of electroplated hard chromium to increase the wear and the corrosion properties

Abstract We have investigated the effect of plasma nitriding and plasma nitrocarburizing on the microstructure and properties of electroplated chromium. Plasma nitriding and plasma nitrocarburizing are applied to 15–100 μm thick electroplated hard chromium coatings to increase both the wear and the corrosion resistance. The properties of the plasma-modified hard chromium layers are characterized by measuring the wear resistance with a Taber wear tester and the corrosion resistance with a salt spray fog test. Cyclic voltammetry is performed in a standard electrochemical cell using a 0.5 M H2SO4 solution acidified to pH 0.3. The compound layer after plasma nitriding consists of CrN and Cr2N with a maximum hardness of about 1100 HK0.01. After plasma nitrocarburizing, Cr3C2 and Cr7C3 are formed. After plasma nitrocarburizing, the maximum hardness is increased up to 2200 HK0.01. The wear rate is reduced as compared to an untreated chromium layer. The exposure time in the salt spray fog, before corrosion products are visible can be increased by a factor of 5. The improvement in wear and corrosion resistance after plasma nitriding and plasma nitrocarburizing is discussed considering microstructural changes of the treated layer.

Pigment dispersion degree and its evolution in storage

The current size of individual particles in most pigments is usually below 1μm; this ensures powerful forces of attraction causing the particles to cling to one another forming aggregates. If pigment dispersion stability is not appropriate, particles join again and form flocculates. It is important to know the initial degree of dispersion, its evolution during coating storage and the influence on its dry film anticorrosive properties. Several anticorrosive coatings were formulated starting from an epoxy resin as binder, tin tannates as inhibitor and a red iron oxide‐micronised talc mixture as inert pigment. Variables studied were pigment dispersion time and coating ageing time in storage. The degree of dispersion was determined by optical photomicroscopy to establish the shape and size of associated particles present in the system. The flow properties of anticorrosive coatings due to the different dispersion degree were evaluated through rheological tests. Coating film behaviour was also assessed for several dispersion times and ageing periods in laboratory, employing a salt spray (fog) cabinet and a 100 per cent relative humidity chamber.

自然換気型細霧冷房温室の温湿度環境

Temperature and humidity environments inside an evaporative-fog air cooling greenhouse with natural ventilation were measured on a clear day in summer. The fog was sprayed intermittently (spraying time: 1 min at 3 or 4-min intervals) from nozzles installed 2 m above the floor inside the greenhouse. The side, end, and roof ventilators of the greenhouse remained open to increase air circulation and fog evaporation during cooling. The results of the experiment are summarized below. (1) The inside air temperature reduced to approximately the inside wet bulb temperature within 1 min after the start of fog spraying. (2) The vertical air temperature differences below the nozzles (plant growing zone) were within 1 °C, and the horizontal air temperature differences at 1.5 m above the floor in the greenhouse cooled with fog spray system were within 2.5°C. (3) The reduction of leaf temperature of the tomato plant by fog spray was smaller than that of air temperature. The difference between the leaf temperature and the air temperature inside the greenhouse decreased as the saturation deficit of the air increased. (4) From these measurements, when fog fills the greenhouse atmosphere, the air is rapidly cooled at a rate of 10°C per min, a small sensor, such as a small diameter thermocouple in which heat capacity is small, is recommended to prevent errors in measuring air temperature.

Coiled-Tubing Applications for Blowout-Control Operations

Coiled-tubing drilling is now being used in various operations. Its complete field of applications is not currently established. Coiled tubing used for well control while drilling is a new field where its limits are being explored. This paper provides guidelines on topics to be considered in determining the applicability of coiled tubing for well-control problems. The information provided is based on recent field experiences with several well-control problems when drilling vent and relief wells. In some cases, coiled-tubing drilling capabilities, by necessity, were significantly extended beyond levels the industry considered to be upper limits. Well control cannot always be handled by coiled tubing. It is a special-application tool that can handle many situations and is, in some cases, clearly the optimum choice for the application. This paper presents guidelines for selecting coiled tubing for each application and discusses economics. It also describes coiled-tubing operations for regaining control of blowout wells in certain situations and gives technical requirements for planning and executing these types of jobs. Case histories where coiled-tubing units (CTU`s) have been used to regain control of drilling and producing wells are provided for illustration.