Automotive paint is the paint used in cars for protection and decoration purposes. Water-based polyurethane acrylic enamel paints today are the most widely used paints for a variety of reasons including reducing the environmental impact of paint.
Modern car paint is applied in several layers, with a total thickness of about 100 Ã,Âμm (0.1mm). The paint application requires preparation and primary steps to ensure proper application. The base layer is applied after the primary paint is applied. After this, paint clearcoats can be applied that form glossy and transparent layers. The clearcoat layer should be able to withstand UV rays.
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History
In the early days of the car industry, paint was applied manually and dried for weeks at room temperature. When the mass production of the car begins, the paint is dried in the oven. Currently, paint is usually applied by a robotic arm and dried in just a few hours.
Until decades ago, lead, chromium and other heavy metals were used in automotive paint. Environmental legislation has banned this, which has resulted in a move to water-based paint. Up to 85% varnish paint can evaporate into the air, polluting the atmosphere. The enamel paint is better for the environment and replaces the varnish paints in the late 20th century. Polyurethane acrylic water-based polyelethane is now almost universally used as a base coating with clearcoat.
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Process and layers
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High pressure water jet spray directed to the body. Without proper pretreatment, premature failure of the finish system can almost be guaranteed. The phosphate layer is required to protect the body from corrosion effects and prepare the surface for E-Coat.
Body dipped in Electro-Coat Paint Operation (ELPO/E-Coat), then high voltage applied. The body acts as a cathode and paints as an anode attached to the surface of the body. This is an environmentally friendly painting process. In E-Coat, also called CED paint, the utilization is about 99.9% and has a good salt spray life test compared to other painting processes.
Primary
Primer is the first layer used. The primary primary function is to act as leveling and shielding, and make the base layer easier to apply to the components used. Primary serves several purposes. It serves as a leveling, which is important because the cabin often has markings and other forms of surface defects after being produced in the workshop. A smoother surface is made by flattening these defects and therefore a better end product. It serves as a protector, the primer will protect from corrosion, heat difference, bumps, rock-chip, UV-light, etc. It also enhances the ease of application by making it easier to stick to surfaces, the more varied ranges the paint can use.
Base Coat
The base layer is applied after the primary layer. This jacket contains the visual properties of colors and effects, and is usually referred to as paint. The base layer used in automotive applications is usually divided into three categories: solid, metallic, and pearlescent pigments.
- Solid paint has no sparkle effect except the color. This is the easiest type of paint to apply, and the most common type of paint for heavy transport vehicles, construction equipment and airplanes. It is also widely used on cars, trucks, and motorcycles. Clear coat was not used in solid colors until the early 1990s.
- Metallic paint contains aluminum flakes to create sparkling and coarse effects, commonly referred to as metallic displays. This paint is more difficult to manage than solid paint because of the extra dimensions to consider. Metallic and pearlescent paints should be applied evenly to ensure consistent finish without light and dark spots often called "spotted". The base layer of the metal is formulated so that the aluminum flakes are parallel to the substrate. This maximizes "failure". This is the difference in brightness between looking perpendicular to the paint and at a sharp angle. The "flop" is maximized if basecoat increases viscosity shortly after application so that the aluminum flakes are in random orientation after spraying is locked into this position while there is still plenty of solvent (or water) in the coating. Subsequent evaporation of the solvent (or water), causes a decrease in the film thickness of the drying layer, causing the aluminum flakes to be dragged into orientation parallel to the substrate. This orientation should not be affected by the application of clear coat coatings. The formulations of the clear layers should be chosen carefully so as not to "dissolve" the base layer and thereby affect the orientation of the metal flakes but will still show sufficient adhesion between the layers to avoid delamination of the clear layer.. Similar action mode occurs with pearlescent pigmented basecrates.
- Pearl paint contains special color pigments commonly referred to as "pearls". The pearl pigments provide a colored glow on the finish that serves to create color depth. Pearlescent paint can be two stages in nature (clear pearl base color) or 3 stages in nature (pearl-coat clear-coat pearl basecoat).
Clearcoat
Usually sprayed over colored basecoats, clearcoat is a glossy and transparent layer that forms the final interface with the environment. For this reason, clearcoats should be durable enough to withstand abrasion and are chemically stable enough to withstand UV rays. Clearcoat can be either solvent or water-borne.
One part and two parts formulations are often referred to as 1k and 2k respectively. OEM (original equipment manufacture) clear coats applied to car metal bodies are usually 1K systems because they can be heated to about 140 degrees C for healing effects. Clear coats applied to plastic components such as bumpers and wing mirrors are 2K systems because they typically can only receive temperatures of up to about 90 degrees C. The 2K system is usually applied "off line" with a coated plastic part mounted on a painted metallic body. Due to differences in the formulations of 1K and 2K systems and the fact that they are coated in different locations they have different effects on "re-dissolution" of the base layer of the metal. This is most easily seen in light metallic paint such as silver and light blue or green in which the "fail" difference is most pronounced.
Terminology
The terminology for automotive paint has been driven by technological developments and by the desire to both differentiate new technologies and connect with previous technologies for the same purpose. Modern car paint is almost always an acrylic polyurethane "enamel" with a pigmented base layer and a clear top layer. These can be described as "acrylic", "acrylic enamel", "urethane", etc. And clearcoat in particular can be described as varnish. True lacquers and acrylic lacquers are worn out and plain acrylic enamels are mostly replaced for performance reasons. Real enamel is not automotive paint. The term is common to any glossy paint that is difficult but its use in the automotive industry is often limited to older paint before the introduction of polyurethane fasteners.
References
- Automotive Paint and Coating , Streitberger & amp; DÃÆ'¶ssel, 2008
- Hans-Joachim Streitberger; Karl-Friedrich Dossel (March 31, 2008). Automotive Paint and Coating . John Wiley & amp; Children. ISBN: 978-3-527-30971-9.
Source of the article : Wikipedia
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