Invar, Kovar, Alloy 42, 42-6, 46, 48 & 52, Rod, Sheet, Plate, Strip/Coil|
Alloys used where metal must form hermetic seal with glass or ceramic (vacuum/power tubes, lamps); or where specific expansion must be met over a certain temperature range (hermetic sealing, optoelectronics, optical/laser benches, composite tooling).
When deciding what kind of paint is best when re-finishing a car, there are lots of factors to consider. Obviously, the aesthetic appeal is of utmost importance—no one wants a paint job to look sloppy— but other things to keep in mind include the application process, drying time, potential health hazards, and base-coat and finishing options. Acrylic and urethane are both common automotive paints, but have distinct and significant differences.
Urethane paints are a industry standard for automive paint, and for the past two decades have mostly replaced acrylic paints as automakers’ preferred choice. Although it is difficult to replicate authentic factory paint nowadays, and neither acrylic nor urethane paint offers that option, many car restorers argue that urethane provides a nicer-looking finish. Urethane paints are extremely durable, and resist chipping—when properly maintained, a coat of urethane paint will outlast most acrylic paints.
In terms of application, urethane paints are easier to apply. Using a pressurized spray can, they provide better coverage than acrylic paints. Tinted primers can be applied to reduce the risk of the top coat appearing thin or light. Additionally, urethane paints are activated by hardeners, meaning once mixed they must be used or the product is wasted. The benefit, however, is that applied urethane dries quickly, cutting down on time spent waiting between coat applications.
It is common practice to follow a base-coat urethane with a clear coat, however some clear coats tint the color, especially if it is black or white. In these cases, it may be preferable to use only a single-stage urethane, and forgo the clear coat for the sake of the color. It is also possible to wet-sand urethane before applying a clear coat.
Urethane paints are toxic and should be used with caution. Because they contain iscocyanantes, airborne compounds that enter the lungs or skin, investigating proper precautions and aerating techniques is important when working with urethan e.
Acrylic paints differ from urethane in that they are water-based. This means the resin adheres to the product using water as its primary agent, whereas urethane depends on a solvent. In this sense, acrylic paint is far less toxic than urethane. Hardeners and other added chemicals are unnecessary, so acrylic paint is ready to go: simply put in a spray-can and apply. The application process, however, is slightly different than urethane, as acrylic paint tends to emerge in smaller droplets.
Acrylic lacquer paints can run high when it comes to cost, approximately 250 dollars a gallon—whereas acrylic enamel can be purchased for less, at about 100 to 150 dollars per gallon. The drying process is much slower than urethane paints, and leaving a coat to sit for 24 to 48 hours before applying another coat is recommended. Because acrylic paint is lighter than urethane, careful consideration should also be used when selecting a primer. Acrylic enamel is more affordable than acrylic lacquer and urethane, making it a common choice for quick-fix jobs. Additionally, acrylic enamel is much more affordable.
Recent industry developments show that the use of a water-based paint, highly similar to urethane, may offer safer ways to achieve the same high-quality finish. Companies like Auto Air Colors are offering non-toxic and affordable alternatives—their paints’ performance is already just as good as urethane, and can withstand the same amount of wear and tear.
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