Advances in the research of inormeric nanomaterial modified polyurethane anti-corrosion coatings

Steel is widely used in automobiles, household appliances, commercial machinery, heavy construction, marine ships and chemical industry and other fields, in the construction and construction of most of the good performance, low-cost low-carbon steel, but steel corrosion is usually the most important cause of industrial accidents and natural resource consumption. Therefore, it is important to prevent steel corrosion. Anti-corrosion coatings, cathode protection method, the use of preservatives and other means to prevent steel corrosion, including anti-corrosion coatings because of a wide range of choices, adaptability, construction convenience, the shape and size of the construction object less restrictions, economic and practical advantages, steel corrosion is a common method
C.
.
Polyurethane (PU) anti-corrosion coating is a mixture of polyurethane film-forming substances, pigments, solvents, additives, is an extremely wide range of coatings, and the introduction of nanomaterials as fillers into polyurethane anti-corrosion coatings can make it obtain good elasticity, barrier, flame retardant, scratch/wear resistance, optical properties and electrical properties, and the corrosion resistance of the coating has a greater improvement. Existing reports of nanomaterials that enhance coating corrosion resistance include TiO
2
, ZnO, SiO
2
, Fe
3
O
4
, Al
2
O
3
, CaCO
3
, ZrO
2
, Cr
2
O
3
, MnAl
2
O
4
, nano-polyphenylamine, graphene and laminated clay, etc. In this paper, the research progress of inormeric nanomaterial modified polyurethane anti-corrosion coatings will be reviewed, focusing on ZnO, TiO
2
, SiO
2
and graphene modified polyurethane anti-corrosion coating system.
1 nm ZnO modified polyurethane anti-corrosion coating
It is well known that coating effectiveness in corrosive environments depends primarily on the protective properties of the coating, adhesion and erosion of the corrosive environment. The protective properties of the coating mainly depend on the tightness of the coating and its bonding with the substrate. NanoZnO has catalytic degradation, anti-migration, shielding ultraviolet, antibacterial anti-virus, anti-aging and other special properties, so the use of nano ZnO anti-migration properties, it can be introduced into polyurethane can increase the denseness of the coating, reduce the transfer of corrosive electrolytes, thereby improving the corrosion resistance of polyurethane, but also can give polyurethane coating other functions.
El Saeed and others prepared ZnO particles with an average particle size of 20 nm using direct precipitation, and then distributed ZnO nanoparticles evenly in the two-part polyurethane substrate by ultrasonic crushing. The results show that with the increase of ZnO content in polyurethane, the corrosion resistance of composite coating is enhanced, and when ZnO content is 2.0%, the corrosion resistance of composite coating is optimal.
Rashvand, etc., introduces 3.0% nanoZnO into a water-based polyurethane substrate to prepare nanocomposing emulsions, which are then coated to phosphate plates using cathode electrophoresis. The results showed that the coated steel plate was still not corroded after soaking 120 d in NaCl solution (3.5%).
in order to improve the dispersion of nanoZnO in polyurethane substrates and enhance the interface compatible between the two phases, nanoZnO is often modified with modifiers. Christopher and others used sodium alginate and litopic sulfonate modified nano ZnO respectively under ultrasound, and then prepared water-based polyurethane/modified ZnO nanocomposing coating through solution mixing. The results show that with the increase of the proportion of modified ZnO in water-based polyurethane, the dispersion of ZnO and the anti-corrosion performance of nano-composite coatings are improved, and the anti-corrosion properties of composite coatings prepared with ligand sulfonate-modified ZnO are better than among compound coatings prepared with sodium alginate modified ZnO. The team also introduced ionic acid-modified nano ZnO (OA-ZnO) into water-based polyurethane substrates to prepare water-based polyurethane/ZnO nanocomposing coatings. The results show that when the OA-ZnO content is 0.3%, the corrosion resistance of the composite coating is the best.
nano ZnO can improve the corrosion resistance of the coating, on the one hand, because of its excellent interface effect and anti-migration, good dispersion of nano ZnO has a large than the surface area and small size, ZnO particle size is smaller, than The larger the surface area, the stronger the interface between it and polyurethane, the better the compatible between the two, so that the denseness of the coating film increased, corrosive media in the coating of the transmission path is longer, resulting in longer corrosion time, resulting in anti-corrosion effect. On the other hand, by changing the nanoZnO, it can be hydrophobic, and with the increase of nano ZnO dosing, the water contact angle of the coating film increases, thus reducing corrosion.
2 nm SiO
2
modified polyurethane anti-corrosion coating
nomethiO
2
and the resin's function group can form a physical chemical intersection point by adsorption or reaction, thus introducing Si-O-Si and Si-O-C bonds into the molecular chain, becoming a three-dimensional network structure. Since the Si-O bond can be 372 kJ/mol, much larger than the C-C bond energy (334 kJ/mol), it has a spiral structure, is highly curly, and the intermolecules have smaller forces, while nanoSiO2 can absorb ultraviolet light, through visible light, has good force properties and heat resistance, so the use of nanoSiO2 modified polyurethane coating to improve its corrosion resistance has broad prospects.
Mills and others doped nanoSiO
2
into polyurethane to investigate the effect of curing temperature on the corrosion resistance of composite coatings. The results showed that the penetration performance of polyurethane was improved after the introduction of 5% nanoSiO
2
, and the high curing temperature was beneficial to the improvement of the corrosion resistance of composite coatings. This is because as the curing temperature increases, the crosslinking density
nanoSiO
2 and polyurethane increases. High crosslink density polymers have an equal electrochemical properties, resulting in high ion resistance, preventing ions from touching the substrate and preventing ions from moving between yin and yang diodes, thus improving corrosion resistance. In addition to introducing nanoSiO
2
directly into polyurethane coatings, nanoSiO
2
can also be modified, then introduced into polyurethane coatings, or by introducing nanoSiO
2
pre-bodies into polyurethane coatings, and then in-place generation, with the aim of improving the stability of nanoSiO
2
in polyurethane-based dispersion. Dolatzadeh and other three hydrophobic silicone alkane coupled agents (R972, R812 and R805) modified nanoSiO
2
, respectively, and then dispersed in polyurethane to prepare polyurethane / SiO
2
nano composite coating. The results showed that nanoSiO2 modified with 8% R812 and 6% R805 improved the corrosion resistance of polyurethane most significantly. Chen Yingmin and others used silane coupled agent KH-570, dispersant BYK-163 and titanium ester coupled agent NDZ-201 to modifie nanoSiO2, and then use it in polyurethane coatings to improve corrosion resistance. Ghosal and others add ethyl tetrasilrate (TEOS) to soy glyceroid monoester polyurethane (SMG-PU) with an in-place SMG-PU/SiO2 nano-composite coating. The results show that the SMG-PU/SiO2 nanomet composite coating (3.8891×10
-10
to 6.875 6×10
-9
A.cm
-2
) compared to SMG-PU coating (1.815 9×10
-8
-9.9 1396×10
-7
A.cm
-2
) and Bare Steel (8.9131×10
-5
The
to 8.1731×10
-4
A.cm
-2
) has a lower corrosion current, and its corrosion protection is shown in Figure 1.
1 Soy Glycero monoester polyurethane and soybean glyceride polyurethane/nano-silicon dioxide composite coating corrosion-proofing
nometer SiO
2
improves coating corrosion resistance The structure is similar to that of nano ZnO, i.e. excellent hydrophobicity after the change can prevent water vapor from touching the coating, while nanoSiO2 has a large surface area and small size, resulting in a dense coating, thus playing a corrosion-proof effect. The difference between the two is that nanoSiO
2
has higher environmental stability than nano ZnO, and nanoSiO
2
and polymers more easily formed cross-linking network resulting in strong coating adhesion, so nanoSiO
2
has an advantage in improving corrosion resistance.
3 nano-clay modified polyurethane anti-corrosion coating
-layer clay is a kind of layered substance formed by the static action of negatively charged sheet layer on the surface and exchangeable cation, inter-layer exchangeable cation can be The exchange reaction with other organic cations increases the layer spacing, which facilitates the formation of nanocomposates between monomer or organic polymer insertion layers, so it has gas barrier, which can prevent the flow of oxygen, thus improving the corrosion resistance of polyurethane coatings.
Ashhari and others have prepared polyurethane/clay nanocomposed coatings through ultrasound, which have better corrosion resistance than pure polyurethane coatings, and have a resistance of about 9.002 G s after soaking 225 d in 3.5% NaCl solution, compared to pure polyurethane coatings, which are only 97 k? Yeh and other coconut oilamide sulfonized beets for the organicization of soil, and then through the water solution dispersion technology to synthesize the water-based polyurethane / monsoton nano-composite coating, and its anti-corrosion effect was studied electrochemically, found that the composite coating containing 3% soiled anti-corrosion effect is good. Moradi and others use 3-amino propylene trimethylsilane modified clay, and prepared polyurethane / clay nano-composite coatings. When the clay content is only 0.5%, the nano-composite coating has a resistance of 8 Gω after soaking 2 h in 3.5% NaCl solution, and the steel plate coated with nano-composite material is exposed to 17 d in 5% NaCl salt spray with slight signs of corrosion.
compared with nano ZnO and nanoSiO
2
, layered clay has a higher long diameter ratio, which can further delay the transmission of corrosive media, delay corrosion rate and enhance the anti-corrosion effect of coating. However, due to the small layer spacing between layered clay sheet layers, when the polymer is composited with it, most of them can only form conventional phase separation material or layer type and peeling type coexisting material, so the anti-corrosion effect has not fully played out. The ideal result is a layered clay that is completely dispersed in the polymer in the form of a single layer, i.e. a completely stripped nanocomposus.
4 Graphene modified polyurethane anti-corrosion coating
Graphene is a two-dimensional layered material formed by the hybridization of single-layer carbon atom sp
2
, with a honeycomb-like crystal structure. Each lattic has 3 keys σ, which are very closely connected to form a stable positive hexagon structure. Because of its oversized surface area, excellent osmosis, high thermal stability and chemical stability, it can effectively block the passing of gas atoms such as water and oxygen, so it has great potential in the metal anti-corrosion coating. On the other hand, the commonly used polymer coating is easy to scrape, and graphene has excellent mechanical properties and friction resistance, can improve the material's weight reduction, wear resistance. Therefore, the use of graphene modified polyurethane coating is a very good choice.
studies have shown that graphene has better properties than layered clay, so it has lower gas penetration at the same load rate. In addition, graphene in the coating arrangement, type, dosing and so on on the anti-corrosion properties of the coating also have different effects. Li and other titanium to the functional change of graphene, and then prepared a water-based polyurethane / graphene nano-composite coating, when the amount of graphene is 0.4%, the composite coating corrosion resistance is the best, its corrosion-proofing concept is shown in Figure 2.
Figure 2 Titanium functional fossil ink/polyurethane composite coating corrosion protection (a) any three-dimensional distribution of titanium acid functional fossil ink (b) surface alignment distribution of titanium acid functional ink
The difference is that when any three-dimensional distribution of TGO reaches a certain amount, it will form an obstacle network structure, so that part of the coating will be sealed, reducing the penetration of the electrolyte. The in-face alignment distribution is the use of TGO surface area as a barrier, multi-layer TGO barrier will increase anti-corrosion performance, which is related to its dispersion.
In order to improve the dispersion of graphene in polyurethane and maximize its corrosion protection, Mo and other functional graphene (FG) and functional graphene oxide (FGO) modified polyurethane coatings. The results show that the dispersion and compatibility of graphene oxide and graphene in polyurethane can be improved by chemical change. Graphene and graphene oxide can effectively enhance the wear and corrosion resistance of polyurethane coatings, and graphene oxide shows better friction resistance than graphene, but the corrosion resistance is less than graphene. Ramezanzadeh and others using polycyanate (PI) sterilizing modified graphene oxide, and then the PI-GO into polyurethane in the preparation of nano-composite coatings, and the introduction of non-modified graphene oxide samples were compared, found that the composite coating containing 0.1% PI-GO corrosion resistance and resistance to ions better. Li and others added graphene oxide, reduced graphene oxide (RGO) and functional graphene to the water-based polyurethane, and found that the compound coating had the best anti-corrosion effect when the RGO content was 0.2%.
is known from above,