Coating classification: inorganic zinc rich coating

Core tip: the earliest zinc rich inorganic coating was invented by Victor Nightingale, an Australian in the 19th century Time of inorganic zinc rich coating in the 19th century Development history The study of using zinc powder to make corrosion-resistant coating was initially carried out in two different places Paint knowledge | precautions for wall paint color selection Recommended introduction: when painting the wall, the owner sometimes has difficulty in choosing what color of the wall paint to paint In fact, there is no ugly color in the wall paint, only the disharmonious color matching The use of wall color contains the knowledge of health Too strong color will stimulate people's perception, make people have a sense of fidgety, affect people's mental health Grasp the basic principles of wall color and paint a colorful space 1、 Wall paint color selection notice 1 Light color is generally used for the top surface Light colors make people feel light, dark colors make people feel heavy Usually, the treatment of rooms is from top to bottom, from shallow to deep For example, the ceiling and walls of rooms are white and Home of coatings: the earliest inorganic zinc rich coating was invented by Victor Nightingale, an Australian in the 19th century The first heating curing inorganic zinc rich coating was prepared by adding zinc powder into water glass In the 19th century, the role of shielding and the history of chemical development in the field of electrochemical protection, the research of using zinc powder to make corrosion-resistant coating was initially carried out in two different places with different ideas British use zinc powder to add organic paint to provide organic zinc rich coating, while Australian use inorganic zinc rich material Victor Charles ninghtingall, an Australian engineer, applied silicate zinc rich coating to part of the woro Nora pipeline project of Sydney's water supply system in 1942 after a long period of painstaking research So far, zinc rich coating began to be used on a large scale In the early 1950s, American improved and developed the post curing inorganic zinc rich coating At the end of 1970s, alcohol soluble self curing inorganic zinc rich coatings were developed in the world Especially with the progress of modern industry and society, the production of coating emphasizes the 4E principle more and more, "economy" is (economy), "efficiency", "ecology" and "energy" People pay more and more attention to environmental protection, so water-based coatings are more and more valued Although there are many disadvantages and technical difficulties in the use of water-based zinc rich coatings in the field of heavy anti-corrosion, water-based coatings have the trend of gradually replacing the existing solvent based coatings At the same time, with the passage of time and the gradual improvement of technology, the solvent based coatings will also be replaced The main anti-corrosion mechanisms are: shielding, electrochemical protection, self-healing and passivation (1) The shielding effect of zinc rich coatings depends on the formation of insoluble salts and corrosion products The traditional zinc rich coating uses spherical zinc powder, which transmits electrons in the form of point contact and keeps electric contact with steel substrate Due to the point contact, the conductivity of the coating is poor In order to improve the conductivity of the coating, a large amount of zinc powder must be added At this time, the volume concentration of zinc powder far exceeds CPVC, and the binder is not enough to fill the gap between the coatings, thus forming a porous coating structure At present, when many zinc powders change from granular to flake, the physical shielding effect is strengthened, because the addition of flake zinc powder increases the penetration distance, at the same time, numerous small areas are formed in the coating, reducing the difference of thermal expansion coefficient between the coating and the metal matrix, reducing the shrinkage rate when the coating is hardened, the stress inside the coating, and inhibiting the cracking and peeling of the coating As a result, the adhesion and the resistance to medium penetration of the coating are improved, and the corrosion resistance of the coating is improved The corrosion products of zinc vary with different corrosion media, including zinc oxide, zinc hydroxide, basic zinc carbonate, basic zinc oxide, zinc sulfate, etc due to the formation of these substances, the volume expands, filling the gap of the coating film, so as to prevent further contact between the iron surface and harmful media such as oxygen and water, playing a physical shielding role At the same time, these corrosion products can make the coating closely combined, increase the resistance, slow down the rate of electrochemical corrosion, the consumption rate of zinc powder will be greatly reduced, and its durability will be improved (2) The zinc rich coating contains a lot of zinc powder The zinc particles are in close contact with the surface of iron and steel The potential of zinc is more negative than that of iron Therefore, in the electrolyte solution, zinc atoms are easy to lose electrons and become anode, while iron is cathode In anode area, zinc is eroded because of losing electrons In cathode area, the surface of iron and steel is protected by electrons In order to make the film conductive to play the role of sacrificial anode, the whole coating must have good conductivity, so that the whole coating and steel substrate system form an electrochemical circuit, zinc rich coating can play an electrochemical protection role (3) The self repairing function of the coating film, when parts of the coating are mechanically damaged, the base metal is exposed, and the corrosion current can flow to the exposed part of the steel in a small area, then the product of zinc is deposited here to form a protective film, delaying the corrosion (4) Passivation: the coating has a good passivation effect on steel The pH value of the coating changes with the evaporation of water during the film-forming process of the coating The electrode potential of the steel substrate is not always in the state of electrochemical protection, so the coating has a good passivation effect on the steel substrate Kinds of inorganic zinc rich coatings are mainly used for anticorrosion The first one is the original formula of sodium water glass (sodium hydroxide) plus zinc powder After potassium water glass, now the lithium water glass made by the new process has developed to today, its composition and process have been complicated and excellent In addition to the filler zinc powder, the types and composition of pigments are also colorful, and the composition of film-forming base material is more complex In addition, the increase of auxiliary (curing agent) also makes it divided into post solid type and self-solid type There are two types of inorganic zinc rich coatings, solvent type and water-based Solvent based inorganic zinc rich coating is based on tetraethyl orthosilicate, because tetraethyl orthosilicate can be dissolved in organic solvent After spraying, alkoxy group in tetraethyl orthosilicate absorbs water in the air and hydrolyzes when the solvent volatilizes, and crosslinks and solidifies into high molecular siloxane polymer That is to say, the process of hydrolysis and polycondensation of ethyl silicate to form a network polymer coating Water based inorganic zinc rich paint is soluble in water at the initial stage of film formation, but after curing, it has excellent water resistance and can be soaked in water for a long time Because of its no organic solvent, no peculiar smell, no combustion and no explosion, simple construction process, low comprehensive cost, easy cleaning of construction tools, no pollution to the environment, long anti-corrosion period, at the same time, some kinds of low porosity, it can be used as hot spraying zinc surface sealer, which has the potential to replace the traditional hot spraying zinc (aluminum) In addition, it has good conductivity and can be welded and cut with paint It is also inferior to organic epoxy zinc rich paint It is a new generation of environmental protection paint with more potential Compared with the traditional hot spraying zinc with mature technology, the advantages of water-based inorganic zinc rich are more prominent First of all, hot spraying zinc is the sacrificial anode protection of a single zinc layer, and its corrosion resistance speed only depends on the thickness and dissolution speed of the zinc layer; in addition to the protection of zinc layer, inorganic zinc rich can better cover the metal surface with lithium silicate, zinc silicate, basic carbonate, etc generated by its complex chemical changes Secondly, the porosity of hot spraying zinc is higher (generally 3% - 5%) and needs to be coated with another sealer; while the porosity of water-based inorganic zinc rich paint film is lower (generally less than 1%), so it can be used as hot spraying zinc surface sealer Moreover, the process of hot spraying zinc is complex and needs high temperature and high pressure device, while inorganic zinc rich can be sprayed and brushed flexibly In general, inorganic zinc rich has lower comprehensive cost Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,