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Report describes tests of paints (primers and topcoats) for use in recoating rusted carbon steel for protection against further corrosion. Paints selected for evaluation all designated by manufacturers as suitable for application over tightly adhering rust.
This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 1 covers spacecraft design considerations for the space environment; advanced composites; polymers; adhesives; metals; ceramics; protective coatings; and lubricants, greases, and seals.
This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 2 covers thermal control systems, power systems, optical components, electronic systems, and applications.
The paper describes application of two modern experimental techniques, thin-film thermocouples and pressure sensitive paint, to measurement in turbine engine components. A growing trend of using computational codes in turbomachinery design and development requires experimental techniques to refocus from overall performance testing to acquisition of detailed data on flow and heat transfer physics to validate these codes for design applications. The discussed experimental techniques satisfy this shift in focus. Both techniques are nonintrusive in practical terms. The thin-film thermocouple technique improves accuracy of surface temperature and heat transfer measurements. The pressure sensitive paint technique supplies areal surface pressure data rather than discrete point values only. The paper summarizes our experience with these techniques and suggests improvements to ease the application of these techniques for future turbomachinery research and code verifications.
It is already known that polyaniline (an electroactive polymer) functions as a corrosion inhibitor for steel and in view of the fact that it is known to perform in the presence of hydrochloric acid, it has been considered likely that it may be useful to NASA for protecting launch structures at KSC which are exposed to not only continual ocean-side salt spray but also to hydrochloric acid at the times that solid-fuel boosters are fired. The currently used zinc-rich silicate-bonded coating is not wholly protective against the hydrochloric acid. Water pollution from zinc salts is another concern. Other earlier and concurrent NASA sponsored projects have been focussed on polyaniline specifically. Our project, administered for NASA by Dr. K. Thompson of KSC and these more-specifically polyaniline-related projects are included in a CRADA coordinated by Dr. F. Via of Akzo Nobel. A parallel project at Polytechnic under Prof K. Levon concentrated more specifically on polyaniline with various dopants. Our exploratory project reported herein was aimed at broadening the range of such corrosion inhibitors, to give protective paint compounders a wider latitude for adding corrosion inhibitors having polyaniline-like performance, and thus we diverged in several probing directions from polyaniline. Our working hypothesis was that physical variants of polyaniline, such as supported formulations on pigments or carriers, and chemical variants of polyaniline, including those having no electroconductive character, may have enhanced anticorrosion activity. We also hypothesized that small (non-polymeric) molecules having structures related to those occurring in polyaniline, may be active as corrosion inhibitors. We did preliminary testing, using an ASTM salt spray method at a nearby commercial paint testing laboratory. Our most interesting findings were that a non-electroconductive meta-isomer of polyaniline showed some corrosion activity, suggesting that the features of the polyaniline molecule associated with conductivity are not necessary for the anticorrosion action. Also, signtficantly, small molecular weight aromatic diamines and diimines resembling the reduced and the oxidized repeating unit in polyaniline showed an interesting degree of anticorrosive activity, suggesting that the polymeric feature of polyaniline is not necessary for anticorrosion action.
Many popular and widely used paint stripping products now contain methylene chloride as their active ingredient. However, the Environmental Protection Agency (EPA) will critically curb the use of methylene chloride under an aerospace national emission standard for hazardous air pollutants (NESHAP) within the next 2-1/2 years. An effort is underway to identify and evaluate alternative depainting technologies emphasizing those believed to be both effective and environmentally benign. On behalf of the EPA and in cooperation with the U. S. Air Force (USAF), the National Aeronautics and Space Administration (NASA) is conducting a technical assessment of nine alternative technologies (i.e.: chemical stripping, two CO2 blasting processes, FLASHJET(TM) coating removal, laser stripping, plastic media blasting, sodium bicarbonate wet stripping, high-pressure water stripping, and wheat starch blasting). These depainting processes represent five removal method categories, namely abrasive, impact, cryogenic, thermal, and/or molecular bonding dissociation. This paper discusses the test plan and parameters for this interagency study. Several thicknesses of clad and non-clad aluminum substrates were used to prepare test specimens, which have been cut, cleaned, painted, and environmentally aged. Each depainting process has been assigned a specimen lot, which is now undergoing an initial strip cycle. Metallurgical impacts will be determined after these specimens complete five cycles of preparation and stripping.
An experimental study was made to obtain quantitative information on heat transfer, flow, and pressure distribution in a branched duct test section that had several significant features of an internal cooling passage of a turbine blade. The objective of this study was to generate a set of experimental data that could be used for validation of computer codes that would be used to model internal cooling. Surface heat transfer coefficients and entrance flow conditions were measured at nominal entrance Reynolds numbers of 45,000, 335,000, and 726,000. Heat transfer data were obtained by using a steady-state technique in which an Inconel heater sheet is attached to the surface and coated with liquid crystals. Visual and quantitative flow-field data from particle image velocimetry measurements for a plane at midchannel height for a Reynolds number of 45,000 were also obtained. The flow was seeded with polystyrene particles and illuminated by a laser light sheet. Pressure distribution measurements were made both on the surface with discrete holes and in the flow field with a total pressure probe. The flow-field measurements yielded flow-field velocities at selected locations. A relatively new method, pressure sensitive paint, was also used to measure surface pressure distribution. The pressure paint data obtained at Reynolds numbers of 335,000 and 726,000 compared well with the more standard method of measuring pressures by using discrete holes.
In January 1998 during, the STS-89 mission, an eight section Russian solar array panel was retrieved after more than ten years exposure to the orbital space environment on the Russian space station Mir. Two darkened handrail samples from the Russian solar array have been evaluated for contamination: a section of a white paint covered rigid handrail and a section of woven fabric over-wrapped around a flexible handhold. The handrail samples were evaluated using optical microscopy (OM), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). Optical properties were also obtained. Microscopy has shown the discolored areas to have thick layers of contaminant that has crazed and spalled off in regions. Energy dispersive spectroscopy revealed that the brown contaminant is composed of oxidized silicon. No silicon was present on the unexposed fabric over-wrap, and very small amounts were present in the white paint. Therefore, the contaminant layer on both samples is attributed to silicone contamination from other spacecraft materials that have been oxidized by atomic oxygen while in orbit. A significant source of the silicone contamination appears to be from the solar array itself.
Catastrophic wildfires, such as the 1990 Painted Cave Fire in Santa Barbara or Oakland fire of 1991, attest to the destructive potential of fire in the wildland/urban interface. For example, during the Painted Cave Fire, 673 structures were consumed over a period of only six hours at an estimated cost of 250 million dollars (Gomes et al., 1993). One of the primary sources of fuels is chaparral, which consists of plant species that are adapted to frequent fires and may actually promote its ignition and spread of through volatile organic compounds in foliage. As one of the most widely distributed plant communities in Southern California, and one of the most common vegetation types along the wildland urban interface, chaparral represents one of the greatest sources of wildfire hazard in the region. An ongoing NASA funded research project was initiated in 1994 to study the potential of AVIRIS for mapping wildfire fuel properties in Southern California chaparral. The project was initiated in the Santa Monica Mountains, an east-west trending range in western Los Angeles County that has experienced extremely high fire frequencies over the past 70 years. The Santa Monica Mountains were selected because they exemplify many of the problems facing the southwest, forming a complex mosaic of land ownership intermixed with a diversity of chaparral age classes and fuel loads. Furthermore, the area has a wide diversity of chaparral community types and a rich background in supporting geographic information including fire history, soils and topography. Recent fires in the Santa Monica Mountains, including several in 1993 and the Calabasas fire of 1996 attest to the active fire regime present in the area. The long term objectives of this project are to improve existing maps of wildland fuel properties in the area, link AVIRIS derived products to fuel models under development for the region, then predict fire hazard through models that simulate fire spread. In this paper, we describe the AVIRIS derived products we are developing to map wildland fuels.
Spacecraft in low Earth orbit (LEO) are subject to degradation in thermal and optical performance of components and materials through interaction with atomic oxygen and vacuum ultraviolet radiation which are predominant in LEO. Due to the importance of LEO durability and performance to manufacturers and users, an international test program for assessing the durability of spacecraft materials and components was initiated. Initial tests consisted of exposure of samples representing a variety of thermal control paints and multilayer insulation materials that have been used in space. Materials donated from various international sources were tested alongside a material whose performance is well known such as Teflon FEP or Kapton H for multilayer insulation, or Z-93-P for white thermal control paints. The optical, thermal or mass loss data generated during the test was then provided to the participating material supplier. Data was not published unless the participant donating the material consented to publication. This paper presents a description of the types of tests and facilities that have been used for the test program as well as some examples of data that have been generated. The test program is intended to give spacecraft builders and users a better understanding of degradation processes and effects to enable improved prediction of spacecraft performance.
During a test at the NASA Glenn Research Center's 1 x 1 Supersonic Wing Tunnel, it was discovered that particles entrained in the air flow were damaging the pressure sensitive paint on a test article. An investigation found the source of the entrained particles to be rust on the internal surfaces of the air supply piping. To remedy the situation, the air supply line components made from carbon steel were either refurbished or replaced with new stainless steel components. The refurbishment process included various combinations of chemical cleaning, bead blasting, painting and plating.
Alternate alkaline and neutral chemical paint strippers have been identified that, with respect to corrosion requirements, perform as well as or better than a methylene chloride baseline. These chemicals also, in general, meet corrosion acceptance criteria as specified in SAE MA 4872. Alternate acid chemical paint strippers have been identified that, with respect to corrosion requirements, perform as well as or better than a methylene chloride baseline. However, these chemicals do not generally meet corrosion acceptance criteria as specified in SAE MA 4872, especially in the areas of non-clad material performance and hydrogen embrittlement. Media blast methods reviewed in the study do not, in general, adversely affect fatigue performance or crack detectability of 2024-T3 substrate. Sodium bicarbonate stripping exhibited a tendency towards inhibiting crack detectability. These generalizations are based on a limited sample size and additional testing should be performed to characterize the response of specific substrates to specific processes.
This is the final report discussing the work done for the Space Environments and Effects (SEE) Program. It discusses test chamber design, coating research, and test results on electrically thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude higher electrical conductivity than most available thermal control coatings. Most current coatings tend to have a range in surface resistivity from 1,011 to 1,013 ohms/sq. Historically, spacecraft have had thermal control surfaces composed of dielectric materials of either polymers (paints and metalized films) or glasses (ceramic paints and optical solar reflectors). Very seldom has the thermal control surface of a spacecraft been a metal where the surface would be intrinsically electrically conductive. The poor thermal optical properties of most metals have, in most cases, stopped them from being used as a thermal control surface. Metals low infrared emittance (generally considered poor for thermal control surfaces) and/or solar absorptance, have resulted in the use of various dielectric coatings or films being applied over the substrate materials in order to obtain the required optical properties.
The effects of linear, diamond, and parabolic fillets on a double delta wing were investigated in the NASA Langley 7 x 10 ft High Speed Tunnel from Mach 0.18 to 0.7 and angles of attack from 4 deg. to 42 deg. Force and moment, pneumatic pressures, pressure sensitive paint, and vapor screen flow visualization measurements were used to characterize the flow field and to determine longitudinal forces and moments. The fillets increased lift coefficient and reduced induced drag without significantly affecting pitching moment. Pressure sensitive paint showed the increase in lift is caused by an increase in suction and broadening of the vortex suction footprint. Vapor screen results showed the mixing and coalescing of the strake fillet and wing vortices causes the footprint to broaden.
In image-based measurements, quantitative image data must be mapped to three-dimensional object space. Analytical photogrammetric methods, which may be used to accomplish this task, are discussed from the viewpoint of experimental fluid dynamicists. The Direct Linear Transformation (DLT) for camera calibration, used in pressure sensitive paint, is summarized. An optimization method for camera calibration is developed that can be used to determine the camera calibration parameters, including those describing lens distortion, from a single image. Combined with the DLT method, this method allows a rapid and comprehensive in-situ camera calibration and therefore is particularly useful for quantitative flow visualization and other measurements such as model attitude and deformation in production wind tunnels. The paper also includes a brief description of typical photogrammetric applications to temperature- and pressure-sensitive paint measurements and model deformation measurements in wind tunnels.
Chromosome translocations are persistent indicators of prior exposure to ionizing radiation and the development of 'chromosome painting' to efficiently detect translocations has resulted in a powerful biological dosimetry tool for radiation dose reconstruction. However, the actual stability of the translocation frequency with time after exposure must be measured before it can be used reliably to obtain doses for individuals exposed years or decades previously. Human chromosome painting probes were used here to measure reciprocal translocation frequencies in cells from two tissues of 8 rhesus monkeys (Macaca mulatta) irradiated almost three decades previously. Six of the monkeys were exposed in 1965 to whole-body (fully penetrating) radiation and two were unexposed controls. The primates were irradiated as juveniles to single doses of 0.56, 1.13, 2.00, or 2.25 Gy. Blood lymphocytes (and skin fibroblasts from one individual) were obtained for cytogenetic analysis in 1993, near the end of the animals' lifespans. Results show identical dose-response relationships 28 y after exposure in vivo and immediately after exposure in vitro. Because chromosome aberrations are induced with identical frequencies in vivo and in vitro, these results demonstrate that the translocation frequencies induced in 1965 have not changed significantly during the almost three decades since exposure. Finally, our emerging biodosimetry data for individual radiation workers are now confirming the utility of reciprocal translocations measured by FISH in radiation dose reconstruction.
Atomic oxygen treatment has been investigated as an unconventional option for art restoration where conventional methods have not been effective. Exposure of surfaces to atomic oxygen was first performed to investigate the durability of materials in the low Earth orbit environment of space. The use of the ground based environmental simulation chambers, developed for atomic oxygen exposure testing, has been investigated in collaboration with conservators at a variety of institutions, as a method to clean the surfaces of works of art. The atomic oxygen treatment technique has been evaluated as a method to remove soot and char from the surface of oil paint (both varnished and unvarnished), watercolors, acrylic paint, and fabric as well as the removal of graffiti and other marks from surfaces which are too porous to lend themselves to conventional solvent removal techniques. This paper will discuss the treatment of these surfaces giving an example of each and a discussion of the treatment results.
The space shuttle wing leading edge and nose cap are composed of a carbon/carbon composite that is protected by silicon carbide. The coefficient of thermal expansion mismatch leads to cracks in the silicon carbide. The outer coating of the silicon carbide is a sodium-silicate-based glass that becomes fluid at the shuttles high reentry temperatures and fills these cracks. Small pinholes roughly 0.1 mm in diameter have been observed on these materials after 12 or more flights. These pinholes have been investigated by researchers at the NASA Johnson Space Center, Rockwell International, the Boeing Company, Lockheed Martin Corporation, and the NASA Glenn Research Center at Lewis Field to determine the possible sources and the extent of damage. A typical pinhole is illustrated in the photomicrographs. These pinholes are found primarily on the wing leading edges and not on the nose cap, which is covered when the orbiter is on the launch pad. The pinholes are generally associated with a bead of zincrich glass. Examination of the orbiter and launch structure indicates that weathering paint on the launch structure leads to deposits of zinc-containing paint flakes on the wing leading edge. These may become embedded in the crevices of the wing leading edge and form the observed zinc-rich glass. Laboratory experiments indicate that zinc oxide reacts vigorously with the glass coating on the silicon carbide. Thus, it is likely that this is the reaction that leads to pinhole formation (Christensen, S.V.: Reinforced Carbon/Carbon Pin Hole Formation Through Zinc Oxide Attack. Rockwell International Internal Letter, RDW 96 057, May 1996). Cross-sectional examination of pinholes suggests that they are enlarged thermal expansion mismatch cracks. This is illustrated in the photomicrographs. A careful microstructural analysis indicates that the pinhole walls consist of layers of zinc-containing glass. Thus, pinholes are likely formed by zinc oxide particles lodging in crevices and forming a corrosive zinc-rich glass that enlarges existing cracks. Having established the likely source of the pinholes, we next needed to model the damage. Our concern was that if a pinhole went through the silicon carbide to the carbon/carbon substrate, oxygen would have a clear path to oxidize the carbon at high temperatures. This possibility was examined with studies in a laboratory furnace. An ultrasonic drill was used to make artificial pinholes in a sample of protected carbon/carbon. After exposure, the specimens were weighed and cross-sectioned to quantify the extent of oxidation below the pinhole. The results at higher temperatures showed good agreement with a simple diffusion-control model. This model is based on the two-step oxidation of carbon to carbon monoxide and carbon dioxide. The fluxes are illustrated in the final figure. The model indicates a strong dependence on pinhole diameter. For smaller diameters and short times, the oxidation of carbon is very limited.