Automotive paint

Automotive paint is paint used on automobiles for both protection and decoration purposes. Water-based acrylic polyurethane enamel paint is currently the most widely used paint for reasons including reducing paint's environmental impact.
Modern automobile paint is applied in several layers, with a total thickness of around 100 µm(0.1mm). Paint application requires preparation and primer steps to ensure proper application. A basecoat is applied after the primer paint is applied. Following this, a clearcoat of paint may be applied that forms a glossy and transparent coating. The clearcoat layer must be able to withstand UV light.
History.
In the early days of the automobile industry, paint was applied manually and dried for weeks at room temperature because it was a single component paint that dried by solvent evaporation. As mass production of cars made the process untenable, paint began to be dried in ovens. Nowadays, two-component (catalyzed) paint is usually applied by robotic arms and cures in just a few hours either at room temperature or in heated booths.
Until several decades ago lead, chromium, and other heavy metals were used in automotive paint. Environmental laws have prohibited this, which has resulted in a move to water-based paints. Up to 85% of lacquer paint can evaporate into the air, polluting the atmosphere. Enamel paint is better for the environment and replaced lacquer paint in the late 20th century. Water-based acrylic polyurethane enamels are now almost universally used as the basecoat with a clearcoat.
Processes and coatings.
Preparation.
High-pressure water spray jets are directed to the body. Without proper pretreatment, premature failure of the finish system can almost be guaranteed. A phosphate coat is necessary to protect the body against corrosion effects and prepares the surface for the E-Coat.
The body is dipped into the Electro-Coat Paint Operation (ELPO/E-Coat), then a high voltage is applied. The body works as a cathode and the paint as an anode sticking on the body surface. It is an eco-friendly painting process. In E-Coat, also called CED paint, utilization is approximately 99.9% and provides superior salt spray resistance compared to other painting processes.
Primer.
The primer is the first coat to be applied. The primer serves several purposes.
Base Coat.
The base coat is applied after the primer coat. This coat contains the visual properties of color and effects, and is usually the one referred to as the paint. Base coat used in automotive applications is commonly divided into three categories: solid, metallic, and pearlescent pigments.
Clearcoat.
Usually sprayed on top of a colored basecoat, clearcoat is a glossy and transparent coating that forms the final interface with the environment. For this reason, clearcoat must be durable enough to resist abrasion and chemically stable enough to withstand UV light. Clearcoat can be either solvent or water-borne.
One part and two part formulations are often referred to as "1K" and "2K" respectively. Car manufacturer (OEM) clear coats applied to the metal bodies of cars are normally 1K systems since they can be heated to around 140 °C to effect cure. The clear coats applied to the plastic components like the bumpers and wing mirrors however are 2K systems since they can normally only accept temperatures up to about 90 °C. These 2K systems are normally applied "off line" with the coated plastic parts fixed to the painted metallic body. Owing to the difference in formulation of the 1K and 2K systems and the fact they are coated in different locations they have a different effect on the "redissolving" of the metallic base coat. This is most easily seen in the light metallic paints like the silver and light blue or green shades where the "flop" difference is most marked.
Terminology.
The terminology for automotive paints has been driven by the progression of technologies and by the desire to both distinguish new technologies and relate to previous technologies for the same purpose. Modern car paints are nearly always an acrylic polyurethane "enamel" with a pigmented basecoat and a clear topcoat. It may be described as "acrylic", "acrylic enamel", "urethane", etc. and the clearcoat in particular may be described as a lacquer. True lacquers and acrylic lacquers are obsolete, and plain acrylic enamels have largely been superseded by better-performing paints. True enamel is not an automotive paint. The term is common for any tough glossy paint but its use in the automotive industry is often restricted to older paints before the introduction of polyurethane hardeners.
Types & Form.
Innovations are taking place in paint industry as well. These days, automotive paints come in liquid form, spray form, and powder forms:-
Types of Automotive Paints
How to paint over chrome.
You can prepare a chrome bumper for paint washing with soap and water, wiping with a waxy material, and using sandpaper to remove any rusty content from the surface of a chrome bumper. You can also spray self-etching primer before applying paint.