Anticorrosive coatings are widely used in the petrochemical industry; after interacting with industry professionals from various companies and conducting assessments of these companies...

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Anti-corrosion coatings are widely used in the petrochemical industry. Through interactions with industry professionals from various companies and investigations of these firms, it was found that there are several misconceptions regarding the practical application of anti-corrosion coatings: 1. Emphasis on anti-corrosion materials while neglecting surface treatment: ① Before applying anti-corrosion coatings to metal or non-metallic materials, it is necessary to pre-treat the surface of the substrate. This is a very important step in the anti-corrosion coating process; improper surface treatment can directly affect the adhesion of the coating to the substrate, the quality of the coating, its protective capabilities, its service life, and its appearance. Analysis shows that the quality of surface treatment is the main factor affecting the quality of the coating. ②Surveys of several major petrochemical companies show that the main factor preventing anti-corrosion coatings from achieving the designed service life is usually inadequate surface treatment; this accounts for over 50% of the problems related to material selection, compatibility, and environmental conditions. This is especially true for steel structures as well as uninsulated storage tanks, reactors, and the outer walls of pipes in plant areas. In some cases, pitting occurs on the steel structures of pipe racks and the outer walls of storage tanks within just six months, while extensive rusting starts within less than a year, resulting in the discharge of yellowish liquid. ③The relevant parties are only concerned with the quality of anti-corrosion coatings, their performance in industry applications, and their economic benefits; they ignore the requirements related to surface treatment. They even attribute the basic surface treatment requirements we put forward to the harsh conditions under which the anti-corrosion coatings are applied. As a result, they are reluctant to invest money or effort in surface treatment, which inevitably leads to a **shorter lifespan of the anti-corrosion protection. 2. Emphasis on material selection, neglect of anti-corrosion compatibility: ① Since anti-corrosion coatings have varying properties, different choices should be made depending on the environmental conditions, the characteristics of the surface to be coated, the construction conditions, and the desired lifespan of the anti-corrosion protection. Therefore, it is not sufficient to simply judge anti-corrosion coatings as “good” or “bad”; rather, they should be selected as part of a whole system, that is, with regard to their compatibility. ②Supporting considerations include factors related to external conditions as well as those related to the coating itself, such as the properties of the substrate to be coated, the reapplication suitability of the base, intermediate, and top coats, corrosion conditions, the film-forming/curing conditions of the coating, surface treatment requirements, the coating thickness, painting methods, the design lifespan for corrosion protection, and technical and economic indicators. ③In actual business practices, it is common to see a lack of attention to the completeness of the anti-corrosion system. In some projects, high-quality anti-corrosion coatings are used, designed for long-term corrosion protection – consisting of an epoxy zinc-rich primer, an epoxy intermediate coat, and a polyurethane top coat – yet the surface treatment relies only on power grinding to achieve ST2/ST3 standards, or even just electric steel/copper brushes for surface cleaning; such methods are completely insufficient to meet the requirements for long-term corrosion protection over 8 years or more ； Some surface treatments use sandblasting to achieve a Sa2.5 standard, yet red lead is used as the primer – \"wearing a dress while wearing straw sandals\"” ； Especially in maintenance work, when repainting over existing coatings without considering the compatibility between the new coating and the old one, problems such as delamination and bubbling occur, leading to failed painting. 3. Focusing on the unit price of materials while neglecting the overall cost: ① In comparison, anti-corrosion coatings with better performance, produced by large manufacturers such as AKZO NOBEL’s international brand paints and Haihong Laoren’s Laoren brand paints, have higher production costs due to factors such as restrictions on the choice of raw materials and the technical complexity of the products; as a result, their price per liter (kilogram) is higher. However, since many of these products are high-solid-content products, they allow for a larger coating area at a given thickness, meaning that the overall cost of the anti-corrosion coating isn’t high under the same design thickness requirements, while the quality improves significantly. Therefore, in the technical and economic comparison of anti-corrosion coatings, attention should also be paid to the coating area and the lifespan of the coating. ②There are many factors that influence the cost of anti-corrosion coatings in anti-corrosion construction; these can be summarized as: designed film thickness, performance specifications of the coating (such as solid content), coating loss, and application methods. ③In business transactions with users, some of them often pay attention only to the unit price of the materials and do not calculate the overall cost; as a result, they choose low-cost anti-corrosion coatings produced by small factories. Such coatings have poor quality, a low solid content, and a limited coating area, which means that the total cost in the end is not low at all. This phenomenon is extremely common. 4. Emphasis on short-term investments and neglect of long-term costs: ① “Corrosion prevention maintenance is needed every year, though the scale varies,” is the author’s humorous remark regarding corrosion control in the petrochemical industry. Investigations conducted by the author among several large petrochemical companies show that more than 70% of the steel structures in these facilities start to rust after three years; after five years, they are almost unrecognizable. The steel structures in pipe racks also become heavily corroded after five years, and the same situation applies to pipelines without insulation. ②When selecting a corrosion protection coating system, a technical and economic comparison should be conducted. Different corrosion resistance lifespans should be assigned to various projects, in order to avoid choosing systems with excessively short lifespans. Such systems may seem to have low initial costs, but they result in high maintenance expenses; due to the complexity of such maintenance, the costs associated with subsequent maintenance for many projects can even exceed the initial investment. ③The corrosion resistance life after maintenance is usually not as good as that achieved by using a coating system with a longer service life at the time of construction. In the total investment of petrochemical projects, corrosion protection accounts for a relatively small proportion; therefore, to ensure the long-term operation of the facilities, it is entirely feasible to choose a coating system with a longer lifespan, thereby reducing the need for subsequent repairs. This approach helps avoid disruptions in normal production due to inadequate corrosion protection, as well as increased maintenance costs.