The Difference Between Paint and Coating
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Scientific Definition of Coatings and Paints: Correcting the Equivalent Concept，Although the topic of coatings and paints has been discussed for many years, there is still no unified, scientific, and standardized definition. Within the industry, coatings and paints have always been understood as equivalent concepts. Therefore, in the terminology clauses of national standards, there is only a standard for the term "coating"; however, outside the industry, the two are often regarded as separate products belonging to different categories.
These two distinctly different understandings (within and outside the industry) have not only caused confusion about the nature of such products but also led to ambiguity regarding the industry’s scope.
The Evolution of the Concepts of "Coating" and "Paint"
Paint has a long history in China. The term "paint" (youqi in Chinese) originated from the fact that early versions of this material were inseparable from vegetable oils and natural lacquer—hence, "paint" carries a profound historical and ancient cultural connotation. With the continuous development of science and technology, the paint industry has expanded, and the varieties and categories of paints have been constantly innovated.
The term "coating" (tuliao in Chinese) emerged in the 1950s. Within the industry, it has always been considered just another name for the same material as paint. From the 1950s to the 1960s, and even into the 1970s, the industry mostly regarded "coating" as the academic term and "paint" as the common name. At that time, the term "coating" had a somewhat academic flavor, and it seemed that only research institutions could use it in their names, such as "Coating Research Institute" or "Coating Research Laboratory." Meanwhile, all production enterprises were uniformly called "paint factories" (youqi chang), "paint-making factories" (zaoqi chang), or "paint-manufacturing factories" (zhiqi chang).
The confusion between the names "coating" and "paint" began after the 1980s. With the rapid development of economic construction and the booming construction industry, the paint industry was no longer monopolized by the chemical industry system as it had been in the past. A large number of new production plants of the same type in China’s construction system generally used "coating" in their enterprise names. As architectural coating products flooded the market, the term "coating" not only moved out of the "sacred academic palace" but also became misinterpreted by society—due to the fact that architectural coatings are mainly water-based products, the concept of "coating" was one-sidedly equated with "water-based," leading to the misunderstanding that coatings and paints are different materials belonging to two separate industries.
National Standard Interpretation of Coatings and Paints
In the national standard (GB 5206.1) – Basic Terminology for Vocabulary of Paints and Varnishes – "coating" is defined as follows:
A general term for a class of liquid or solid materials that, when applied to the surface of an object, can form a solid film with protective, decorative, or special properties (such as insulation, corrosion resistance, marking, etc.). In the early days, most of these materials used vegetable oils as the main raw material, hence the name "paint." Now, synthetic resins have mostly or completely replaced vegetable oils, so they are called "coatings."
Regarding the above definition, the author has the following two observations:
1.The reason why such materials are now called "coatings" rather than "paints" is largely due to the development of the varieties and categories of paints. The term "paint" can no longer cover all existing products in the industry, while "coating" can fully encompass all product categories in the industry—using the name "coating" is more accurate and scientific.
For example, powder coating products are not suitable to be referred to as "paints"; here, "coating" and "paint" are not interchangeable. Therefore, "coating" can include both solid powder coatings and liquid paints, but the reverse is not true. Thus, the explanation in the standard is not very comprehensive.
2.The "note" to the coating terminology in the standard – "the character ‘qi’ (paint) can be used in the names of specific coating varieties, such as ready-mixed paint, paste paint, etc." – is also somewhat inappropriate. In fact, the character "qi" is not only used in the names of specific coating varieties but also extensively in the categories of coatings (e.g., acrylic paints, polyurethane paints) and in general references to application fields (e.g., anti-corrosion paints, automotive paints, marine paints). Actually, except for a few cases, the terms "coating" and "paint" are interchangeable; the use of "paint" is not limited to specific product varieties.
The Concept of "Coatings = Paints" Needs Correction
The apparent characteristic of "qi" (paint) and "youqi" (paint) is that they are liquid, which cannot cover solid coatings other than liquid ones. Since their coverage scopes are different, it is no longer valid to explain the concepts of coatings and paints as equivalent.
Currently, water-based coatings and powder coatings have become well-established categories—especially architectural coatings, dominated by water-based paints, which account for approximately 38% of the total coating output in China. Due to the fundamental differences in chemical properties between water-based paints and oil-based paints, as well as the significant differences in product characteristics, the outdated understanding that water-based paints are a major branch of the paint industry is unscientific. Water-based paints and oil-based paints should be listed as two distinct series of liquid coatings.
Therefore, the author suggests that in the basic terminology standards, not only should the standard for the term "coating" be appropriately revised, but also terminology standards for "qi" (paint), "youqi" (paint), and "water-based paint" should be established. Their definitions could be:
Coating: A general term for a class of liquid or solid materials that, when applied to the surface of an object, can form a solid film with protective, decorative, or special properties (such as insulation, corrosion resistance, marking, etc.). It includes oil-based paints, water-based paints, and powder coatings.
Qi (Paint): Flowable liquid coatings. It includes oil-based paints and water-based paints.
Youqi (Oil-based Paint): Oil-based paints with organic solvents as the medium, or high-solid, solvent-free oil-based paints.
Water-based Paint: Coatings that can be dissolved or dispersed in water.
