Anticorrosive paint and preparation method thereof

Abstract

The invention discloses an anticorrosive coating and a preparation method thereof. The anticorrosive coating comprises a component A and a component B, the component A is prepared from the following raw materials in parts by weight: 60 to 80 parts of bisphenol A type epoxy resin E-51, 36 to 48 parts of polysulfide rubber, 0.3 to 0.4 part of triphenylphosphine, 8 to 10 parts of reactive diluent, 0.5 to 1 part of wetting dispersant, 0.1 to 0.3 part of defoaming agent, 0.1 to 0.3 part of flatting agent, 10 to 20 parts of mica powder, 20 to 30 parts of talcum powder, 5 to 10 parts of glass powder and 5 to 10 parts of zinc oxide filler; the component B is a curing agent; the weight part ratio of the component A to the component B is (8-10): 1. The curing agent with an alkane long chain, a polyamine structure, an amide structure and an anhydride structure is synthesized by taking tung oil methyl ester as a basic framework, so that a coating film has excellent toughness, water resistance, adhesive force, hardness, high temperature resistance and corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and specifically relates to an anti-corrosion coating and a preparation method thereof. Background Art

[0002] The solvent-free epoxy anti-corrosion coating is composed of resin, diluent, pigment filler, additives, curing agent, etc. It is non-toxic and environmentally friendly. It not only has the excellent properties of solvent-based epoxy resin coatings, but also has good anti-permeation performance and anti-corrosion performance. Metals in high-salt and high-humidity marine environments often need to be protected with heavy anti-corrosion coatings. The heavy anti-corrosion coatings must have good water barrier performance and strong enough adhesion to the metal substrate, and be able to adhere tightly to the metal substrate. Under humid conditions, water will gradually penetrate into the coating, weakening the adhesion between the substrate and the coating, and making the adhesion between the two worse. The coating must have sufficient adhesion to protect the substrate more effectively. Epoxy resin has good adhesion to metal substrates, but its toughness is insufficient.

[0003] The curing agent plays a decisive role in the performance of the epoxy resin anti-corrosion coating. Therefore, a suitable curing agent must be selected. With the increasing depletion of global petrochemical resources and the rising environmental protection calls, the raw materials of chemical products are gradually becoming biomass-based. As a biomass resource, tung oil has renewable properties and more active chemical properties than other vegetable oils. In order to better utilize tung oil, a series of tung oil derivatives, such as tung oil anhydride, methyl tungate, methyl tungate-maleic anhydride adducts, etc., have been studied to facilitate the introduction of tung oil molecules into the polymer chain segments, thereby improving the modification effect of tung oil on polymer materials. Tung oil-based curing agents are still a direction worthy of in-depth study in the epoxy resin curing agent system. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides an anti-corrosion coating and a preparation method thereof.

[0005] The object of the present invention can be achieved by the following technical solutions: An anti-corrosion coating includes component A and component B. Component A includes the following raw materials in parts by weight: 60-80 parts of bisphenol A type epoxy resin E-51, 36-48 parts of polysulfide rubber, 0.3-0.4 part of triphenylphosphine, 8-10 parts of active diluent, 0.5-1 part of wetting and dispersing agent, 0.1-0.3 part of defoaming agent, 0.1-0.3 part of leveling agent, 10-20 parts of mica powder, 20-30 parts of talc powder, 5-10 parts of glass powder, and 5-10 parts of zinc oxide filler; Component B: curing agent; The weight ratio of component A to component B is 8-10:1.

[0006] The active diluent is 1,4-butanediol diglycidyl ether.

[0007] The wetting and dispersing agent is an alkyl ammonium salt acidic copolymer containing hydroxyl functional groups.

[0008] The defoamer is a polysiloxane solution.

[0009] The leveling agent is a polyether-modified polydimethylsiloxane copolymer.

[0010] The curing agent is prepared through the following steps: Step A1: Add tung oil into a three-necked flask, heat up to 60 - 70 °C, add an appropriate amount of methanol solution of potassium hydroxide, stir for 2 - 3 h, add formic acid to stop the reaction, then perform vacuum distillation at 80 °C for 45 - 60 min, let it stand for layer separation, wash the upper oil phase with water 3 - 4 times, and after separation, perform vacuum distillation at 85 °C for 30 - 40 min to remove trace water completely, thus obtaining intermediate a. The dosage ratio of tung oil, methanol solution of potassium hydroxide, and formic acid is 6 g : 1 - 2 g : 0.10 - 0.15 mL. The methanol solution of potassium hydroxide is prepared by mixing potassium hydroxide and methanol in a mass ratio of 7 : 25; During the reaction process, an ester exchange reaction occurs between tung oil and methanol to generate intermediate a. The structure of intermediate a is shown as follows:

[0011] Step A2: In a three-necked flask equipped with a stirrer, a condenser, and a thermometer, add intermediate a, phenol, and aluminum chloride, stir and react at 98 - 103 °C for 2 - 2.5 h, then add diethylenetriamine into the above flask, slowly dropwise add aqueous formaldehyde solution under the condition of 40 - 50 °C, heat up to 85 - 90 °C, stir and react for 2 h, then perform vacuum distillation for 15 - 30 min to obtain intermediate b. The dosage ratio of intermediate a, phenol, aluminum chloride, diethylenetriamine, and aqueous formaldehyde solution is 0.1 mol : 0.033 - 0.050 mol : 0.001 - 0.0015 mol : 0.08 - 0.1 mol : 20 - 35 mL. The mass fraction of the aqueous formaldehyde solution is 37%; During the reaction process, intermediate a and phenol undergo a Friedel - Crafts substitution reaction under the catalysis of aluminum chloride to obtain a product, and the product then undergoes a Mannich reaction with diethylenetriamine and formaldehyde to generate intermediate b. The structure of intermediate b is shown as follows:

[0012] Step A3: Add intermediate b and toluene into a flask, then add diethylenetriamine, heat up to 170 - 180 °C, stir and react for 3 - 3.5 h to obtain intermediate c. The dosage ratio of intermediate b, toluene, and diethylenetriamine is 0.1 mol : 120 - 150 mL : 0.1 - 0.15 mol; During the reaction process, intermediate b and diethylenetriamine undergo an amidation reaction to generate intermediate c. The structure of intermediate c is shown as follows:

[0013] Step A4: Add intermediate c and toluene into a flask, start stirring, then add maleic anhydride, and stir and react at 100 °C for 4 - 5 h. After filtration and drying, a curing agent is obtained. The dosage ratio of intermediate c, toluene, and maleic anhydride is 0.1 mol : 150 - 180 mL : 0.1 mol; During the reaction process, the conjugated diene in intermediate c undergoes a Diels - Alder reaction with maleic anhydride with high selectivity, introducing an anhydride structure into the curing agent molecule. The curing agent molecule also has an alkane long chain, a polyamine structure, and an amide structure, enabling the curing agent to have the advantages of obtaining cured products with high strength, high stiffness, and high - temperature resistance when using acid anhydride - type curing agents, fast curing speed of polyaliphatic amines, and multiple dispersed active sites that can cross - link with epoxy resins. The alkane long chain improves the flexibility and water resistance of the curing agent molecule, and the amide structure introduces the advantages that polyamide - type curing agents have good adhesion to various substrates, excellent adhesion, and can be cured at room temperature.

[0014] Advantages of the present invention: The raw materials of the anti - corrosion coating of the present invention include component A and component B. Component A includes bisphenol A epoxy resin E - 51, polysulfide rubber, triphenylphosphine, active diluent, wetting and dispersing agent, defoaming agent, leveling agent, mica powder, talc powder, glass powder, and zinc oxide filler, and component B is a curing agent. By modifying epoxy resin with polysulfide rubber, the structure of polysulfide rubber with good molecular chain flexibility is introduced into the epoxy resin, playing a toughening role and making the coating film have good toughness. The synthesized curing agent uses methyl eleostearate, a derivative of the bio - based raw material tung oil, as the basic skeleton, and through a series of reactions, a curing agent with an alkane long chain, a polyamine structure, an amide structure, and an anhydride structure is prepared. The alkane long chain improves the flexibility and water resistance of the curing agent molecule, enhancing the toughness and water resistance of the coating film; polyaliphatic amines have a fast curing speed and multiple dispersed active sites that can cross - link with epoxy resins, accelerating the drying speed of the coating film; the amide structure introduces the advantages that polyamide - type curing agents have good adhesion to various substrates, excellent adhesion, and can be cured at room temperature, enhancing the adhesion of the coating film; using acid anhydride - type curing agents can obtain cured products with high strength, high stiffness, and high - temperature resistance, enhancing the hardness and high - temperature resistance of the coating film; after curing, a three - dimensional network structure is formed, and it is difficult for oil and deionized water to enter the coating film, so the anti - corrosion performance is excellent. Specific Embodiments

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0016] Example 1 A curing agent is prepared by the following steps: Step A1: Add tung oil into a three-necked flask, heat up to 60 °C, add an appropriate amount of methanol solution of potassium hydroxide, stir and keep the temperature constant for 2 h, add formic acid to stop the reaction, then carry out reduced pressure distillation at 80 °C for 45 min, let it stand for layering, wash the upper oil phase with water 3 times, and after separation, carry out reduced pressure distillation at 85 °C for 30 min to remove trace water completely, thus obtaining intermediate a. The dosage ratio of tung oil, methanol solution of potassium hydroxide and formic acid is 6 g: 1 g: 0.10 mL, and the methanol solution of potassium hydroxide is prepared by mixing potassium hydroxide and methanol according to a mass ratio of 7:25; Step A2: In a three-necked flask equipped with a stirrer, a condenser and a thermometer, add intermediate a, phenol and aluminum chloride, stir and react at 98 °C for 2 h, then add diethylenetriamine into the above flask, slowly dropwise add aqueous formaldehyde solution under the condition of 40 °C, heat up to 85 °C, stir and react for 2 h, then carry out reduced pressure distillation for 15 min to obtain intermediate b. The dosage ratio of intermediate a, phenol, aluminum chloride, diethylenetriamine and aqueous formaldehyde solution is 0.1 mol: 0.033 mol: 0.001 mol: 0.08 mol: 20 mL, and the mass fraction of the aqueous formaldehyde solution is 37%; Step A3: Add intermediate b and toluene into the flask, then add diethylenetriamine, heat up to 170 °C, stir and react for 3 h to obtain intermediate c. The dosage ratio of intermediate b, toluene and diethylenetriamine is 0.1 mol: 120 mL: 0.1 mol; Step A4: Add intermediate c and toluene into the flask, start stirring, then add maleic anhydride, stir and react at 100 °C for 4 h, filter, and obtain the curing agent after drying. The dosage ratio of intermediate c, toluene and maleic anhydride is 0.1 mol: 150 mL: 0.1 mol.

[0017] Example 2 A curing agent is prepared by the following steps: Step A1: Add tung oil into a three-necked flask, heat up to 65 °C, add an appropriate amount of methanol solution of potassium hydroxide, stir and keep the temperature constant for 2.5 h, add formic acid to stop the reaction, then carry out reduced pressure distillation at 80 °C for 50 min, let it stand for layering, wash the upper oil phase with water 3 times, and after separation, carry out reduced pressure distillation at 85 °C for 35 min to remove trace water completely, thus obtaining intermediate a. The dosage ratio of tung oil, methanol solution of potassium hydroxide and formic acid is 6 g: 1.5 g: 0.10 mL, and the methanol solution of potassium hydroxide is prepared by mixing potassium hydroxide and methanol according to a mass ratio of 7:25; Step A2: Add intermediate a, phenol, and aluminum chloride into a three-necked flask equipped with a stirrer, a condenser, and a thermometer. Stir and react at 100 °C for 2.2 h. Then add diethylenetriamine into the above flask, slowly dropwise add an aqueous formaldehyde solution at 45 °C, raise the temperature to 87 °C, stir and react for 2 h, and then perform vacuum distillation for 25 min to obtain intermediate b. The dosage ratio of intermediate a, phenol, aluminum chloride, diethylenetriamine, and the aqueous formaldehyde solution is 0.1 mol: 0.042 mol: 0.0012 mol: 0.09 mol: 28 mL, and the mass fraction of the aqueous formaldehyde solution is 37%; Step A3: Add intermediate b and toluene into a flask, then add diethylenetriamine, raise the temperature to 175 °C, stir and react for 3.2 h to obtain intermediate c. The dosage ratio of intermediate b, toluene, and diethylenetriamine is 0.1 mol: 135 mL: 0.12 mol; Step A4: Add intermediate c and toluene into a flask, start stirring, then add maleic anhydride, stir and react at 100 °C for 4.5 h, filter, and dry to obtain the curing agent. The dosage ratio of intermediate c, toluene, and maleic anhydride is 0.1 mol: 165 mL: 0.1 mol.

[0018] Example 3 A curing agent is prepared by the following steps: Step A1: Add tung oil into a three-necked flask, raise the temperature to 70 °C, add an appropriate amount of a methanol solution of potassium hydroxide, stir and keep the temperature constant for 3 h, add formic acid to stop the reaction, then perform vacuum distillation at 80 °C for 60 min, let it stand for layering, wash the upper oil phase with water 4 times, separate, and perform vacuum distillation at 85 °C for 40 min to remove trace water completely to obtain intermediate a. The dosage ratio of tung oil, the methanol solution of potassium hydroxide, and formic acid is 6 g: 2 g: 0.15 mL, and the methanol solution of potassium hydroxide is prepared by mixing potassium hydroxide and methanol in a mass ratio of 7:25; Step A2: Add intermediate a, phenol, and aluminum chloride into a three-necked flask equipped with a stirrer, a condenser, and a thermometer. Stir and react at 103 °C for 2.5 h. Then add diethylenetriamine into the above flask, slowly dropwise add an aqueous formaldehyde solution at 50 °C, raise the temperature to 90 °C, stir and react for 2 h, and then perform vacuum distillation for 30 min to obtain intermediate b. The dosage ratio of intermediate a, phenol, aluminum chloride, diethylenetriamine, and the aqueous formaldehyde solution is 0.1 mol: 0.050 mol: 0.0015 mol: 0.1 mol: 35 mL, and the mass fraction of the aqueous formaldehyde solution is 37%; Step A3: Add intermediate b and toluene into a flask, then add diethylenetriamine, raise the temperature to 180 °C, stir and react for 3.5 h to obtain intermediate c. The dosage ratio of intermediate b, toluene, and diethylenetriamine is 0.1 mol: 150 mL: 0.15 mol; Step A4: Add intermediate c and toluene into a flask, start stirring, then add maleic anhydride, and stir and react at 100 °C for 5 h. After filtration and drying, a curing agent is obtained. The dosage ratio of intermediate c, toluene and maleic anhydride is 0.1 mol: 180 mL: 0.1 mol.

[0019] Example 4 An anticorrosive coating comprises component A and component B. Component A comprises the following raw materials in parts by weight: 60 parts of bisphenol A epoxy resin E-51, 36 parts of polysulfide rubber, 0.3 part of triphenylphosphine, 8 parts of active diluent, 0.5 part of wetting and dispersing agent, 0.1 part of defoaming agent, 0.1 part of leveling agent, 10 parts of mica powder, 20 parts of talc powder, 5 parts of glass powder and 5 parts of zinc oxide filler; Component B: curing agent; The weight ratio of component A to component B is 8:1; The active diluent is 1,4-butanediol diglycidyl ether, the wetting and dispersing agent is an alkylammonium salt acidic copolymer containing hydroxyl functional groups, the defoaming agent is a polysiloxane solution, and the leveling agent is a polyether-modified polydimethylsiloxane copolymer.

[0020] The anticorrosive coating is prepared by the following steps: Step S1: Under nitrogen protection, add polysulfide rubber into bisphenol A epoxy resin E-51, add triphenylphosphine and stir for 2 h to obtain polysulfide rubber-modified epoxy resin.

[0021] Step S2: Add the polysulfide rubber-modified epoxy resin, active diluent, wetting and dispersing agent, defoaming agent and leveling agent into a reaction kettle, stir for 20 min, then add mica powder, talc powder, glass powder and zinc oxide filler, stir for 30 min, then grind for 2 h by a three-roll grinder and discharge. Add the discharged material and the curing agent into the reaction kettle, stir for 25 min to obtain the anticorrosive coating.

[0022] Example 5 An anticorrosive coating comprises component A and component B. Component A comprises the following raw materials in parts by weight: 70 parts of bisphenol A epoxy resin E-51, 42 parts of polysulfide rubber, 0.35 part of triphenylphosphine, 9 parts of active diluent, 0.8 part of wetting and dispersing agent, 0.2 part of defoaming agent, 0.2 part of leveling agent, 15 parts of mica powder, 25 parts of talc powder, 8 parts of glass powder and 8 parts of zinc oxide filler; Component B: curing agent; The weight ratio of component A to component B is 9:1; The active diluent is 1,4-butanediol diglycidyl ether, the wetting and dispersing agent is an alkylammonium salt acidic copolymer containing hydroxyl functional groups, the defoaming agent is a polysiloxane solution, and the leveling agent is a polyether-modified polydimethylsiloxane copolymer.

[0023] The anticorrosive coating is prepared by the following steps: Step S1: Under nitrogen protection, add polysulfide rubber into bisphenol A epoxy resin E-51, add triphenylphosphine and stir for 2.5 h to obtain polysulfide rubber modified epoxy resin.

[0024] Step S2: Add the polysulfide rubber modified epoxy resin, active diluent, wetting and dispersing agent, defoaming agent and leveling agent into the reaction kettle, stir for 25 min, then add mica powder, talc powder, glass powder and zinc oxide filler, stir for 35 min, then grind for 2 h by a three-roll grinder and discharge. Add the discharged material and the curing agent into the reaction kettle, stir for 30 min to obtain the anticorrosive coating.

[0025] Example 6 An anticorrosive coating comprises component A and component B. Component A comprises the following raw materials in parts by weight: 80 parts of bisphenol A epoxy resin E-51, 48 parts of polysulfide rubber, 0.4 part of triphenylphosphine, 10 parts of active diluent, 1 part of wetting and dispersing agent, 0.3 part of defoaming agent, 0.3 part of leveling agent, 20 parts of mica powder, 30 parts of talc powder, 10 parts of glass powder and 10 parts of zinc oxide filler; Component B: curing agent; The weight ratio of component A to component B is 10:1; The active diluent is 1,4-butanediol diglycidyl ether, the wetting and dispersing agent is an alkylammonium salt acidic copolymer containing hydroxyl functional groups, the defoaming agent is a polysiloxane solution, and the leveling agent is a polyether modified polydimethylsiloxane copolymer.

[0026] The anticorrosive coating is prepared through the following steps: Step S1: Under nitrogen protection, add polysulfide rubber into bisphenol A epoxy resin E-51, add triphenylphosphine and stir for 3 h to obtain polysulfide rubber modified epoxy resin.

[0027] Step S2: Add the polysulfide rubber modified epoxy resin, active diluent, wetting and dispersing agent, defoaming agent and leveling agent into the reaction kettle, stir for 30 min, then add mica powder, talc powder, glass powder and zinc oxide filler, stir for 40 min, then grind for 2 h by a three-roll grinder and discharge. Add the discharged material and the curing agent into the reaction kettle, stir for 35 min to obtain the anticorrosive coating.

[0028] Comparative Example 1 This comparative example is a commercially available anticorrosive coating.

[0029] Comparative Example 2 Compared with Example 6, replace the curing agent with diethylenetriamine, and the others are exactly the same as Example 6 to prepare the anticorrosive coating.

[0030] To test the anticorrosive coating prepared by the present invention, the performance is measured according to relevant standards, and the results are shown in Table 1.

[0031] Table 1:

[0032] According to the data in Table 1, comparing Examples 4, 5 and 6 with Comparative Example 1, it can be seen that compared with the commercially available anti-corrosion coatings, the anti-corrosion coatings prepared by the present invention have excellent toughness, adhesion, hardness, water resistance, heat resistance and salt spray resistance; comparing Example 6 with Comparative Example 2, it can be seen that compared with using a curing agent, using diethylenetriamine to play a curing role results in a decrease in toughness, adhesion, water resistance, heat resistance and salt spray resistance. The absence of the alkane long chain reduces the toughness and water resistance of the coating film; the non-introduction of the amide structure weakens the adhesion of the coating film; the non-introduction of the anhydride structure reduces the high-temperature resistance of the coating film.

[0033] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. An anticorrosive coating, characterized in that: The invention comprises component A and component B, wherein component A comprises the following raw materials in parts by weight: 60-80 parts of bisphenol A epoxy resin E-51, 36-48 parts of polysulfide rubber, 0.3-0.4 parts of triphenylphosphine, 8-10 parts of active diluent, 0.5-1 parts of wetting dispersant, 0.1-0.3 parts of defoamer, 0.1-0.3 parts of leveling agent, 10-20 parts of mica powder, 20-30 parts of talcum powder, 5-10 parts of glass powder and 5-10 parts of zinc oxide filler; component B: curing agent; the weight ratio of component A to component B is 8-10:1; the active diluent is 1,4-butanediol diglycidyl ether, the wetting dispersant is an alkyl ammonium salt acid copolymer containing a hydroxyl functional group, the defoamer is a polysiloxane solution, and the leveling agent is a polyether-modified polydimethylsiloxane copolymer; The curing agent is prepared by the following steps: Step A1: Add tung oil to a three-necked flask, heat to 60-70°C, add an appropriate amount of potassium hydroxide methanol solution, stir and keep the temperature for 2-3h, add formic acid dropwise, and then distill under reduced pressure at 80°C for 45-60min, let stand and separate, wash the upper oil phase with water 3-4 times, and after separation, distill under reduced pressure at 85°C for 30-40min to obtain intermediate a; Step A2: In a three-necked flask equipped with a stirrer, a condenser and a thermometer, add intermediate a, phenol and aluminum chloride, stir and react at 98-103°C for 2-2.5h, then add diethylenetriamine to the flask, slowly dropwise add formaldehyde aqueous solution at 40-50°C, raise the temperature to 85-90°C, stir and react for 2h, and then distill under reduced pressure for 15-30min to obtain intermediate b; Step A3: Add intermediate b and toluene into a flask, then add diethylenetriamine, raise the temperature to 170-180°C, and stir to react for 3-3.5 hours to obtain intermediate c; Step A4: Add intermediate c and toluene into a flask, start stirring, then add maleic anhydride, stir and react at 100° C. for 4-5 hours, filter, and dry to obtain a curing agent.

2. The anti-corrosion coating according to claim 1, characterized in that: In step A1, the usage ratio of tung oil, methanol solution of potassium hydroxide and formic acid is 6g:1-2g:0.10-0.15mL, and the methanol solution of potassium hydroxide is prepared by mixing potassium hydroxide and methanol in a mass ratio of 7:

25.

3. The anti-corrosion coating according to claim 1, characterized in that: In step A2, the usage ratio of intermediate a, phenol, aluminum chloride, diethylenetriamine and formaldehyde aqueous solution is 0.1 mol: 0.033-0.050 mol: 0.001-0.0015 mol: 0.08-0.1 mol: 20-35 mL, and the mass fraction of formaldehyde aqueous solution is 37%.

4. The anticorrosive coating according to claim 1, characterized in that: In step A3, the usage ratio of intermediate b, toluene and diethylenetriamine is 0.1 mol:120-150 mL:0.1-0.15 mol.

5. The anti-corrosion coating according to claim 1, characterized in that: In step A4, the usage ratio of intermediate c, toluene and maleic anhydride is 0.1 mol:150-180 mL:0.1 mol.

6. The method for preparing an anticorrosive coating according to claim 1, characterized in that: Made by the following steps: Step S1: under nitrogen protection, adding polysulfide rubber to bisphenol A epoxy resin E-51, adding triphenylphosphine and stirring for 2-3 hours to obtain polysulfide rubber modified epoxy resin; Step S2: adding polysulfide rubber modified epoxy resin, active diluent, wetting dispersant, defoamer and leveling agent into a reaction kettle, stirring for 20-30 minutes, then adding mica powder, talcum powder, glass powder and zinc oxide filler, stirring for 30-40 minutes, grinding for 2 hours on a three-roll grinder to obtain a material, adding the material and curing agent into a reaction kettle, stirring for 25-35 minutes, and obtaining an anti-corrosion coating.

Images