When you see a car, your first impression probably would be the color of the body. Today, having a beautiful shiny paint is one of the basic standards for automotive manufacturing. But more than a hundred years ago, painting a car was not an easy task, and it was far less beautiful than it is today. How did car paint evolve to the extent it has today? Surley will tell you the history of the development of car paint coating technology.
Ten seconds to understand the full text:
1, Lacquer originated in China, the West led after the industrial revolution.
2, The natural base material paint dries slowly, affecting the efficiency of automotive manufacturing process, DuPont invented fast-drying nitro paint.
3, Spray guns replaces brushes, giving more uniform paint film.
4, From alkyd to acrylic, the pursuit of durability and diversity is ongoing .
5, From "spraying" to the "dip coating" with lacquer bath, the continuous pursuit of the quality of paint comes to phosphating and electrodeposition now.
6, Replacement with water-based paint in pursuit of environmental protection.
7, Now and in the future, the painting technology is becoming more and more beyond imagination, even without paint.
The main role of paint is anti-aging
Most people's perception of the role of paint is to give items brilliant colors, but from an industrial manufacturing point of view, color is actually a secondary need; rust and anti-aging is the main purpose. From the early days of iron-wood combination to the pure metal white body of today, the car body needs paint as a protective layer. The challenges that the paint layer has to face are natural wear and tear such as sun, sand and rain, physical damage such as scraping, rubbing and collision, and erosion such as salt and animal droppings. In the evolution of painting technology, the process is slowly developing more and more efficient and durable and beautiful skins for the bodywork to better meet these challenges.
Lacquer from China
Lacquer has a very long history and, shamefully, the leading position in lacquer technology belonged to China before the Industrial Revolution. The use of lacquer dates back as far as the Neolithic era, and after the Warring States period, craftsmen used tung oil extracted from the seeds of the tung tree and added natural raw lacquer to make a mixture of paints, although at that time lacquer was a luxury item for the nobility. After the establishment of the Ming Dynasty, Zhu Yuanzhang began to set up a government lacquer industry, and paint technology developed rapidly. The first Chinese work on paint technology, "The Book of Painting", was compiled by Huang Cheng, a lacquer maker in the Ming Dynasty. Thanks to the technical development and internal and external trade, lacquerware had developed a mature handicraft industry system in the Ming Dynasty.
The most highly sophisticated tung oil paint of the Ming Dynasty was the key to ship manufacturing. The sixteenth century Spanish scholar Mendoza mentioned in "History of the Greater China Empire" that Chinese ships coated with tung oil had twice the life span of European ships.
In the middle of the 18th century, Europe finally cracked and mastered the technology of tung oil paint, and the European paint industry gradually took shape. The raw material tung oil, besides being used for lacquer, was also an important raw material for other industries, still monopolized by China, and became an important industrial raw material for the two industrial revolutions until the early 20th century, when the tung trees transplanted in North and South America took shape, which broke China's monopoly of raw materials.
Drying no longer takes up to 50 days
In the early 20th century, automobiles were still made using natural base paints such as linseed oil as a binder.
Even Ford, which pioneered the production line to build cars, used only Japanese black paint almost to the extreme in order to pursue manufacturing speed because it dries fastest, but after all, it is still a natural base material paint, and the paint layer still needs more than a week to dry.
In the 1920s, DuPont worked on a fast-drying nitrocellulose paint (aka nitrocellulose paint) that made automakers smile, no longer having to work on cars with such long paint cycles.
By 1921, DuPont was already a leader in the manufacture of nitrate motion picture films, as it turned to nitrocellulose-based non-explosives products to absorb the huge capacity facilities it had built during the war. On a hot Friday afternoon in July 1921, a worker at a DuPont film plant left a barrel of nitrate cotton fiber on the dock before leaving work. When he opened it again on Monday morning, he found that the bucket had turned into a clear, viscous liquid that would later become the basis for nitrocellulose paint. In 1924, DuPont developed DUCO nitrocellulose paint, using nitrocellulose as the main raw material and adding synthetic resins, plasticizers, solvents and thinners to blend it. The biggest advantage of nitrocellulose paint is that it dries quickly, compared to natural base paint which takes a week or even weeks to dry, nitrocellulose paint only takes 2 hours to dry, greatly increasing the speed of painting. in 1924, almost all production lines of General Motors used Duco nitrocellulose paint.
Naturally, nitrocellulose paint has its drawbacks. If sprayed in a humid environment, the film will easily turn white and lose its luster. The formed paint surface has poor corrosion resistance to petroleum-based solvents, such as gasoline, which can damage the paint surface, and the oil gas that leaks out during refueling can accelerate the deterioration of the surrounding paint surface.
Replacement of brushes with spray guns to solve uneven layers of paint
In addition to the characteristics of the paint itself, the painting method is also very important for the strength and durability of the paint surface. The use of spray guns was an important milestone in the history of painting technology. The spray gun was fully introduced into the industrial painting field in 1923 and into the automotive industry in 1924.
The DeVilbiss family thus founded DeVilbiss, a world-renowned company specializing in atomization technology. Later, Alan DeVilbiss' son, Tom DeVilbiss, was born. Dr. Alan DeVilbiss' son, Tom DeVilbiss, took his father's invention beyond the medical field. DeVilbiss took his father's inventions beyond the medical field and transformed the original atomizer into a spray gun for paint application.
In the field of industrial painting, brushes are rapidly becoming obsolete by spray guns. deVilbiss has been working in the field of atomization for more than 100 years and is now the leader in the field of industrial spray guns and medical atomizers.
From alkyd to acrylic, more durable and stronger
In the 1930s, alkyd resin enamel paint, referred to as alkyd enamel paint, was introduced into the automotive painting process. The metal parts of the car body were sprayed with this type of paint and then dried in an oven to form a very durable paint film. Compared to nitrocellulose paints, alkyd enamel paints are faster to apply, requiring only 2 to 3 steps compared to 3 to 4 steps for nitrocellulose paints. Enamel paints not only dry quickly, but are also resistant to solvents such as gasoline.
The disadvantage of alkyd enamels, however, is that they are afraid of sunlight, and in sunlight the paint film will be oxidized at an accelerated rate and the color will soon fade and become dull, sometimes this process can even be within just a few months. Despite their disadvantages, alkyd resins have not been completely eliminated and are still an important part of today's coating technology. Thermoplastic acrylic paints appeared in the 1940s, greatly improving the decorative and durability of the finish, and in 1955, General Motors began painting cars with a new acrylic resin. The rheology of this paint was unique and required spraying at a low solids content, thus requiring multiple coats. This seemingly disadvantageous characteristic was an advantage at the time because it allowed for the inclusion of metal flakes in the coating. The acrylic varnish was sprayed with a very low initial viscosity, allowing the metal flakes to be flattened down to form a reflective layer, and then the viscosity increased rapidly to hold the metal flakes in place. Thus, metallic paint was born.
It is worth noting that this period saw a sudden advance in acrylic paint technology in Europe. This stemmed from the restrictions imposed on the European Axis countries after World War II, which restricted the use of some chemical materials in industrial manufacturing, such as nitrocellulose, a raw material needed for nitrocellulose paint, which could be used to make explosives. With this restriction, companies in these countries began to focus on enamel paint technology, developing an acrylic urethane paint system. when European paints entered the United States in 1980, American automotive paint systems were far from European rivals.
Automated process of phosphating and electrophoresis for the pursuit of the advanced paint quality
The two decades after World War II were a period of increased quality of body coatings. At this time in the United States, in addition to transportation, cars also had the attribute of improving social status, so car owners wanted their cars to look more upscale, which required the paint to look more shiny and in more beautiful colors.
Starting in 1947, car companies began to phosphatize metal surfaces before painting, as a way to improve the adhesion and corrosion resistance of the paint. The primer was also changed from spray to dip coating, which means that the body parts are dipped into a pool of paint, making it more uniform and the coating more comprehensive, ensuring that hard-to-reach locations such as cavities can also be painted.
In the 1950s, car companies found that although the dip coating method was used, a portion of the paint would still be washed off in the subsequent process with solvents, reducing the effectiveness of rust prevention. To solve this problem, in 1957, Ford joined forces with PPG under the leadership of Dr. George Brewer. Under the leadership of Dr. George Brewer, Ford and PPG developed the electrodeposition coating method that is now commonly used.
Ford then established the world's first anodic electrophoretic paint shop in 1961. The initial technology was flawed, however, and PPG introduced a superior cathodic electrophoretic coating system and corresponding coatings in 1973.
Paint to last beautiful to reduce pollution for water-based paint
In the mid to late 70's, the awareness of energy saving and environmental protection brought by the oil crisis also had a great impact on the paint industry. Into the 80s, countries enacted new volatile organic compound (VOC) regulations, which made acrylic paint coatings with high VOC content and weak durability unacceptable to the market. In addition, consumers also expect body paint effects to last at least 5 years, which requires addressing the durability of the paint finish.
With the transparent lacquer layer as a protective layer, the internal color paint does not need to be as thick as before, only an extremely thin layer is needed for decorative purposes. UV absorbers are also added to the lacquer layer to protect the pigments in the transparent layer and the primer, significantly increasing the life of the primer and color paint.
The painting technique is initially costly and is generally used only on high-end models. Also, the durability of the clear coat was poor, and it would soon flake off and require repainting. In the following decade, however, the automotive industry and the paint industry worked to improve the coating technology, not only by reducing the cost but also by developing newer surface treatments that dramatically improved the life of the clear coat.
The increasingly amazing painting technology
Future coating mainstream development trend, some people in the industry believe that no-painting technology. This technology has actually penetrated into our lives, and the shells of everyday to home appliances have actually used no-painting technology. The shells add the corresponding color of nano-level metal powder in the injection molding process, directly forming the shells with brilliant colors and metallic texture, which no longer need to be painted at all, greatly reducing the pollution produced by painting. Naturally, it is also widely used in automobiles, such as trim, grille, rearview mirror shells, etc.
A similar principle is used in the metal sector, which means that in the future, metal materials that are used without painting will already have a protective layer or even a color layer at the factory. This technology is currently used in the aerospace and military sectors, but it is still far from being available for civilian use, and it is not possible to offer a wide range of colors.
Summary: From brushes to guns to robots, from natural plant paint to high-tech chemical paint, from the pursuit of efficiency to the pursuit of quality to the pursuit of environmental health, the pursuit of painting technology in the automotive industry has not stopped, and the degree of technology is getting higher and higher. The painters who used to hold brushes and work in the harsh environment would not expect that today's car paint has been so advanced and is still developing. The future will be a more environmentally friendly, intelligent and efficient era.
Post time: Aug-20-2022
