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Let’s introduce the differences between low-surface-preparation coatings for secondary coating and repair, and rust-covered coatings. Low-surface-preparation coatings used for secondary coating and repair need to be distinguished from rust-covered coatings first; the main purpose of rust-covered coatings is to be applied to surfaces with residual rust, whereas low-surface-preparation coatings can be used not only on surfaces with rust but also on other types of old paint layers. Such coatings are known as surface-tolerant coatings, and they are commonly referred to as low-surface-preparation coatings in the industry. First, we need to understand what is meant by working on surfaces that are rusty. It does not mean applying paint without doing anything to address the surface rust deposits. Regarding minimal surface preparation, we must determine what condition the substrate surface can be in before proceeding; this may include the presence of oxide scales, rust, various old coatings, as well as water, oil, salt, etc. Moreover, the construction environment might feature high or low temperatures, high humidity, and other factors, all of which need to be taken into consideration. Secondly, the use of low-surface-treatment coatings is employed in situations where it is not possible to achieve the Sa2.5 sandblasting standard while still meeting high-level corrosion protection requirements; at the same time, such coatings are required to be able to be applied over various types of existing coatings without causing any compatibility issues. In summary, low-surface-treatment coatings can be used to treat ST2/3 surfaces by hand or with power tools, as well as surfaces with existing coatings or those that have been cleaned by high-pressure water jetting. Since these products are primarily used for maintenance purposes, they must also be more capable of withstanding various climates and unusual operating conditions than other products. The coating must have the following properties: good penetration and adhesion (modified epoxy), good corrosion inhibition (due to pigment addition), minimal impact on existing coatings (high solid content with little effect from solvents), sufficient flexibility (to accommodate expansion of existing coatings), and tolerance to harsh weather conditions (ability to be applied at low temperatures, as well as in conditions of moderate humidity or even with a small amount of water on the substrate).