A salt spray, evaporation corrosion experimental device and method for simulating hot-dip zinc coating in a marine atmospheric environment

Abstract

A kind of salt fog, evaporation corrosion experimental device and method of hot-dip galvanizing coating under simulated marine atmospheric environment, it is related to the field of hot-dip galvanizing coating corrosion experiment, including test box, atomizing mechanism, droplet mechanism and sample heating mechanism arranged in test box;Sample heating mechanism is used to support and heat the sample to be corroded;Droplet mechanism includes droplet pipe suspended above sample, the upper end of droplet pipe extends test box and is communicated with external cooling water tank, water flow control valve is arranged on droplet pipe;Atomizing mechanism includes total liquid pipe, top liquid pipe and top atomizing nozzle arranged on top liquid pipe, both ends of total liquid pipe are respectively communicated with top liquid pipe and salt solution tank outside test box, the number of top atomizing nozzle is multiple and is distributed around droplet pipe.Through the simulation test of the application, the corrosion condition of hot-dip galvanizing layer under marine atmospheric environment is monitored, to provide reference basis for the research of hot-dip galvanizing layer corrosion mechanism and the protective coating setting of heat exchange pipe.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hot-dip zinc coating corrosion experiment, in particular to a salt spray and evaporation corrosion experiment device and method for simulating hot-dip zinc coating in marine atmospheric environment. BACKGROUND

[0002] In the use of the heat exchange pipe in the compound air cooling condenser, the spray heat exchange mode is adopted, the cooling water is directly sprayed outside the pipe, the hot fluid in the pipe is condensed or cooled, the cooling water is directly sprayed on the outer wall of the pipe, so part of the water absorbs the heat of the hot fluid in the pipe and evaporates. In addition, the spray heat exchanger is generally installed in the space where the air flows, and the air also absorbs part of the heat. Due to the cooling of the cooling water and the air, the heat transfer effect is good, and the water consumption is small.

[0003] When the compound air cooling condenser is used in the coastal industrial area, the heat exchanger outer surface, especially the elbow, will appear scaling phenomenon, and with the further aggravation of the scaling phenomenon, corrosion and red rust will occur on the surface of the elbow, and serious corrosion pits will also occur, which will ultimately affect the service life of the heat exchanger.

[0004] In the laboratory conditions, the present application simulates the evaporation corrosion test of the hot-dip zinc coating on the outer surface of the heat exchange pipe in the marine atmospheric environment and the salt spray environment, monitors and analyzes the scaling and corrosion phenomenon mechanism and the development law of the corrosion phenomenon of the hot-dip zinc coating, and provides a reference for the research and protection of the heat exchange pipe. SUMMARY

[0005] The present application aims to provide a salt spray and evaporation corrosion experiment device and method for simulating hot-dip zinc coating in marine atmospheric environment, so as to conduct corrosion test research on the hot-dip zinc coating and improve the accuracy of the test.

[0006] In order to solve the above technical problems, the specific scheme adopted by the present application is as follows: a salt spray and evaporation corrosion experiment device for simulating hot-dip zinc coating in marine atmospheric environment, comprising a test box, an atomization mechanism, a dripping mechanism and a sample heating mechanism arranged in the test box; the sample heating mechanism is used for supporting and heating the sample to be corroded; the dripping mechanism comprises a dripping pipe suspended above the sample, the upper end of the dripping pipe extends out of the test box and is communicated with an external cooling water tank, a water flow control valve is arranged on the dripping pipe; the atomization mechanism comprises a total liquid supply pipe, a top liquid supply pipe and a top atomization nozzle arranged on the top liquid supply pipe, the two ends of the total liquid supply pipe are respectively communicated with the top liquid supply pipe and a salt solution tank outside the test box, the number of the top atomization nozzles is multiple and they are distributed around the dripping pipe.

[0007] As a further optimization of the above technical scheme, the sample is a conical surface structure with the middle part being convex, the middle part of the sample is an experimental area, and the edge is an evaporation area, and the water outlets of the top atomization nozzles and the dripping pipe are both located above the experimental area.

[0008] As a further optimization of the above technical solution, the included angle between the sample cone surface and the bottom surface is 3-10 degrees.

[0009] As a further optimization of the above technical solution, the sample heating mechanism comprises an upper open heat preservation box, a folded heating pad is arranged in the heat preservation box, a heat preservation layer is arranged between the heating pad and the heat preservation box, and the sample is located on the heating pad.

[0010] As a further optimization of the above technical solution, the heat preservation layer is aluminum foil.

[0011] As a further optimization of the above technical solution, a fan for blowing air to the surface of the sample is further arranged on the side wall of the test box.

[0012] As a further optimization of the above technical solution, the atomization mechanism further comprises a side atomization assembly for spraying salt mist from the side of the sample, the side atomization assembly comprises a side liquid pipe surrounding the fan and a side atomization nozzle circumferentially and spaced on the side liquid pipe, and the side liquid pipe is in communication with the total liquid supply pipe providing the salt solution.

[0013] A test method of a salt mist and evaporation corrosion test device for hot-dip galvanized coating based on simulated marine atmospheric environment, characterized in that it comprises the following steps:

[0014] S1: preparing industrial cooling water, salt solution and sample samples for standby;

[0015] S2: placing the sample sample on the sample heating mechanism for heating;

[0016] S3: turning on the atomization mechanism and the liquid drop mechanism, controlling the speed of the liquid drop, and making the liquid drop on the surface of the sample evaporate before the next liquid drop is dropped;

[0017] S4: taking out the sample at regular time to detect the corrosion condition of the sample surface.

[0018] As a further optimization of the above technical solution, the concentration of the salt solution is 5g / L, and the mass ratio of NaNO3:NaCl is 4:1.

[0019] As a further optimization of the above technical solution, the salt mist deposition amount is 1-2ml / 80cm2.16h.

[0020] Compared with the prior art, the beneficial effects of the present application are as follows: through the simulation test of the present application, the corrosion condition of the hot-dip galvanized layer in the marine atmospheric environment is monitored, which provides a reference basis for the research of the corrosion mechanism of the hot-dip galvanized layer and the setting of the protective coating of the heat exchange pipe.

[0021] The present application simulates the corrosion of the hot-dip galvanized sample under the salt spray condition by providing the salt spray environment in the test box, and the cooling water is dropped on the sample surface and evaporates by absorbing the heat of the sample, which is consistent with the working environment of the heat exchanger elbow, and the test result has high accuracy.

[0022] The sample in the present application is provided with a conical surface in the middle part, and the cooling water falling on the sample flows downward along the conical surface, and since the cooling water has low temperature when falling on the sample, the evaporation is weak at this time, and with the downward flow of the cooling water, the evaporation gradually accelerates, and therefore the main evaporation area is concentrated in the edge of the sample; since the water vapor generated by the evaporation of the cooling water flows upward and contacts the downward salt spray, the salt spray concentration is diluted, and in the present application, the atomizing nozzle generating the salt spray corresponds to the middle part of the sample, which can reduce the contact between the salt spray and the rising steam during the downward process of the salt spray, and further reduce the influence of the evaporation of the cooling water on the dense fog of the salt spray contacting the sample, so that the salt spray concentration contacted by the experimental area in the middle part of the sample is consistent with the real working condition, and the observed and analyzed test result is more accurate. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of example 1;

[0024] Figure 2 It is a top view schematic diagram of the sample with a conical surface;

[0025] Figure 3 It is a schematic diagram of the top liquid pipe and the top atomizing nozzle;

[0026] Figure 4 It is a schematic diagram of the side liquid pipe and the side wall atomizing nozzle;

[0027] Figure 5 It is a structural schematic diagram of example 2;

[0028] The drawings show that: 1, test box, 2, sample, 201, experimental area, 202, evaporation area, 3, heating controller, 4, heating pad, 5, aluminum foil, 6, insulation box, 7, liquid pump, 8, salt solution tank, 9, total liquid pipe, 10, top atomizing nozzle, 11, top liquid pipe, 12, base, 13, fixed vertical rod, 14, fixed horizontal rod, 15, clamping part, 16, cooling water tank, 17, water flow control valve, 18, liquid drop pipe, 19, side atomizing nozzle, 20, side liquid pipe, 21, side atomizing control valve, 22, fan, 23, top atomizing control valve. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be further described in detail below in combination with the drawings and specific examples, and the parts not described and disclosed in the following examples of the present application should be understood as the prior art known or should be known by the person skilled in the art.

[0030] Example 1

[0031] like Figure 1 As shown, the present invention discloses a salt spray and evaporative corrosion test device for hot-dip zinc coating under simulated marine atmospheric environment, including test chamber 1, sample heating mechanism, atomization mechanism and dripping mechanism set in test chamber 1.

[0032] The heating mechanism is used to support and heat the sample 2 to simulate the working conditions when the heat exchange tube is in operation and the material to be exchanged is introduced. The heating mechanism includes an insulated box 6 and a heating element installed inside the insulated box 6. The insulated box 6 is a rectangular box made of glass with an open top. The insulated box 6 is installed inside the test chamber 1 and located at the bottom of the test chamber 1.

[0033] The heating element includes a heating pad 4 and a heating controller 3 for controlling the temperature of the heating pad 4. The heating pad 4 used in this embodiment is a commercially available silicone rubber heating pad 4. When in use, the silicone rubber heating pad 4 is folded and then wrapped with aluminum foil 5. The wrapped silicone rubber heating pad 4 is then placed in an insulation box 6. The aluminum foil 5 serves as the insulation layer for the heating element, which can prevent the heat generated by the heating pad 4 from radiating to the surroundings and ensure that the heating pad 4 is maintained within a certain temperature range after heating.

[0034] The upper part of the insulation layer composed of aluminum foil 5 is open, and the sample 2 to be corroded is placed on the silicone rubber heating pad 4. The lower surface of the sample 2 is in contact with the silicone rubber heating pad 4. Due to the temperature of the silicone rubber heating pad 4 itself and the heat retained after being wrapped by aluminum foil 5, the sample 2 can be heated to the target temperature. In this simulation test, the target temperature of the sample 2 is 100-150℃.

[0035] The aluminum foil 5 is used to wrap the silicone rubber heating pad 4 to prevent excessive heat dissipation from the silicone rubber heating pad 4 after heating, which would result in poor heating effect on the sample 2. Alternatively, the heating mechanism can be set to other commercially available heating elements, as long as they can continuously heat the sample 2 to the target temperature.

[0036] The dripping mechanism is suspended above the sample 2 and includes a dripping tube 18. An outlet is located at the lower end of the dripping tube 18, formed by a reduction in the diameter of the tube. Alternatively, a nozzle can be detachably installed at the lower end of the dripping tube 18. The upper end of the dripping tube 18 extends outside the test chamber 1 and connects to the cooling water tank 16. A water flow control valve 17 is installed on the dripping tube 18, which can adjust the flow rate of the cooling water within the tube, allowing the dripping cooling water droplets to fall gradually onto the upper surface of the sample 2 at a certain flow rate.

[0037] The dripping mechanism is fixed by a bracket on one side of the test chamber 1. The bracket includes a base 12 and a fixed upright 13, with a horizontal fixed crossbar 14 mounted on the upright 13. The dripping tube 18 is a hard glass tube. A through hole is provided at the top of the test chamber 1, through which the dripping tube 18 is inserted into the test chamber 1. A clamping part 15 is provided at the end of the fixed crossbar 14 away from the fixed upright 13. The clamping part 15 is used to clamp the dripping tube 18 to fix its position during operation. The clamping part 15 can be a test tube clamp or a clamp, which is existing technology and will not be described in detail here.

[0038] like Figure 1 , Figure 3 As shown, the atomizing mechanism includes a main infusion pipe 9, a top dispensing pipe 11, and top atomizing nozzles 10 mounted on the top dispensing pipe 11. One end of the main infusion pipe 9 extends into the test chamber 1 and communicates with the top dispensing pipe 11 located inside the test chamber 1. The top dispensing pipe 11 is an annular pipe. The top atomizing nozzles 10 are spaced apart on the top dispensing pipe 11. The other end of the main infusion pipe 9 communicates with a salt solution tank 8 outside the test chamber 1. A pump 7 is installed inside the salt solution tank 8 to deliver the salt solution to the top atomizing nozzles 10. The top atomizing nozzles 10 are used to atomize the salt solution to create a salt spray environment around the sample 2.

[0039] The diameter of the annular top dispensing tube 11 is smaller than the diameter of the sample 2. The outlet of the dripping tube 18 corresponds to the center of the sample 2. The dripping tube 18 passes through the annular top dispensing tube 11. Multiple top atomizing nozzles 10 are distributed around the dripping tube 18.

[0040] like Figure 1 , Figure 2 As shown, sample 2 has an upwardly convex conical structure. During the experiment, the temperature of sample 2 was approximately 100–150°C. Cooling water dripped onto the central convex area of ​​sample 2, flowing downwards along the conical surface. The cooling water was initially at a low temperature upon entering sample 2, resulting in weak evaporation. As the cooling water flowed downwards, evaporation gradually accelerated, thus the main evaporation occurred at the edges of sample 2. The water vapor generated by the evaporation of cooling water flowed upwards, diluting the salt spray concentration. In this invention, the atomizing nozzle generating the salt spray was positioned at the center of the upwardly convex area of ​​sample 2. The salt spray overflowing onto sample 2 mainly fell to the center, while the evaporation of cooling water concentrated at the edges. This reduced the contact between the salt spray and the rising steam during its downward movement, thereby minimizing the impact of evaporation on the concentrated salt spray.

[0041] The angle between the conical surface and the bottom surface of sample 2 is 3 to 10 degrees. The low tilt angle enables the droplets to flow along the conical surface while preventing the droplets falling on the surface of sample 2 from flowing out of sample 2 quickly and affecting the evaporation effect.

[0042] Therefore, the test results of the middle part of the sample 2 are more accurate than those of the edge part, and thus the middle part of the sample 2 is set as the experimental area 201, and the edge part is set as the evaporation area 202. The water outlets of the atomizing spray head 10 and the droplet pipe 18 are located above the experimental area 201.

[0043] In addition, due to the dripping and atomization and the continuous heating of the sample 2 by the sample 2 heating device, the temperature and humidity in the test box 1 change. A temperature and humidity monitor is arranged in the test box 1, and an exhaust fan and a ventilation window are arranged on the side wall of the test box 1 to maintain a certain temperature and humidity in the test box 1. Specifically, the temperature in the test room is maintained at about 35°C, and the humidity is above 95%. The temperature and humidity monitor and the exhaust fan are prior art, and thus will not be described here.

[0044] The embodiment also discloses a test method based on the above-mentioned salt spray and spraying corrosion test device for hot-dip galvanized coating in a simulated marine atmospheric environment, and specifically includes the following steps:

[0045] S1: Prepare industrial cooling water, a salt solution and a sample 2 for standby;

[0046] The prepared industrial cooling water can be the cooling water used by a heat exchange pipe in operation according to prior art. The concentration of the salt solution is 5 g / L, the mass ratio of NaNO3 to NaCl in the salt solution is 4:1, the pH value is 6.5-7.2, and the temperature is 35±2°C. The sample 2 is a steel plate with a hot-dip galvanized coating. The edge of the sample 2 is sealed by an epoxy resin paint to avoid the exposure of the steel plate during cutting, which causes the edge of the sample 2 to be corroded in advance during the test.

[0047] S2: Place the sample 2 on the sample 2 heating mechanism to heat the sample 2 to 100-150°C.

[0048] S3: Start the atomization and droplet test operation, control the speed of the liquid droplets, and make the next liquid droplet drop after the liquid droplets on the surface of the sample 2 evaporate. The salt spray deposition amount is maintained at 1-2 ml / 80 cm2.16h during the test.

[0049] S4: Take out the sample 2 at regular time intervals to check the corrosion of the surface of the sample 2.

[0050] Specifically, the sample 2 is taken out every 2 hours to analyze the fouling and corrosion of the surface of the sample 2 until the hot-dip galvanized layer of the sample 2 is completely corroded and red rust is generated. The composition of the fouling and corrosion products of the sample 2 at each time interval is analyzed and recorded.

[0051] Through the test, the corrosion progress of each stage can be analyzed, and the maintenance of the heat exchange tube can be provided. The test sample 2 used in the test is a conical test sample 2 with an upward protrusion in the middle. When analyzing the test results, the test results of the middle test area 201 of the test sample 2 are used as the standard.

[0052] In this embodiment, the mass ratio of NaNO3:NaCl in the salt solution is set to 4:1, which is related to the industrial environment of the heat exchange tube being studied. The heat exchange tube is used in the industrial area, and the chemical substances in the gas in the industrial area can form acid rain. Therefore, in order to be closer to the gas phase environment of the industrial area, the content of NaNO3 in the salt solution is higher than that of NaCl. This configuration is closer to the actual working environment of the heat exchange tube when it is applied, and the test results are more accurate.

[0053] Embodiment 2

[0054] The main structure of this embodiment is the same as that of embodiment 1, except that in addition to the top liquid pipe 11 and the top atomizing nozzle 10 in embodiment 1, a fan 22 and a side atomizing mechanism are also provided.

[0055] As shown in Figure 4 , Figure 5 , the fan 22 is arranged on the side wall of the test box 1, and the side atomizing mechanism includes a side liquid pipe 20 surrounding the fan 22 and a side atomizing nozzle 19 arranged on the side liquid pipe 20 in a circumferential direction. The side liquid pipe 20 is in communication with the total liquid pipe 9 for providing the salt solution. The total liquid pipe 9 branches into two branches, which are in communication with the top liquid pipe 11 and the side liquid pipe 20, respectively. The branch in communication with the top liquid pipe 11 is provided with a top atomizing control valve 23, and the branch in communication with the side liquid pipe 20 is provided with a side atomizing control valve 21, so as to realize separate control of the side atomizing operation and the top atomizing operation.

[0056] In addition to the simulation test as in embodiment 1, the top atomizing nozzle 10 can be closed, and the fan 22 and the side atomizing mechanism can be opened in this embodiment. The wind blown by the fan 22 carries the salt mist particles to the test sample, thereby simulating the salt mist and evaporation test under the wind condition of the marine environment.

[0057] The specific test steps are as follows:

[0058] S1: Prepare industrial cooling water, salt solution, and test sample 2 samples, and prepare the wind conditions of the actual working environment of the heat exchange tube for use; the specific steps are the same as those of embodiment 1;

[0059] S2: Place the test sample 2 sample on the test sample 2 heating mechanism, and heat the test sample 2 to 100-150℃;

[0060] S3: open the atomization, droplet test operation, control the speed of liquid drop, make the next droplet drop after the liquid drop on the surface of sample 2 evaporates; specifically, select to close the fan 22 and the side atomization control valve 21, open the top atomization control valve 23, to simulate the salt fog and evaporation experiment under the natural evaporation condition of the marine environment; based on the wind power under the actual working condition environment, select to open the fan 22 and the side atomization control valve 21, close the top atomization control valve 23, to simulate the salt fog and evaporation experiment under the wind regulation;

[0061] S4: take out sample 2 regularly to detect the corrosion condition of the surface of sample 2.

[0062] Specifically, sample 2 is taken out every 2 hours, the fouling and corrosion condition of the surface of sample 2 is analyzed, until the hot-dip galvanized layer of sample 2 is completely corroded, red rust is produced, the composition of the fouling and corrosion product of sample 2 at each period is analyzed and recorded.

[0063] That is, the test device can simulate the corrosion test environment of sample 2 under the natural evaporation state and the test environment under the wind condition, fully consider the real salt fog working condition environment, provide the test results under different environmental conditions, and further improve the accuracy of the test.

[0064] The above only describes the preferred embodiments of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for simulating salt spray, evaporative corrosion testing of hot-dip galvanized coatings in a marine atmospheric environment, characterized in that, It comprises the following steps: S1: preparing industrial cooling water, salt solution, sample (2) sample, standby; S2: placing the sample (2) sample on the sample heating mechanism for heating; S3: opening the atomization mechanism, drop mechanism, controlling the speed of liquid drops, so that the liquid drops on the surface of the sample (2) evaporate and then drop the next drop; S4: take out the sample (2) regularly to detect the corrosion of the sample (2) surface; The concentration of the salt solution is 5 g / L, and the mass ratio of NaNO3:NaCl is 4:1; the salt mist deposition amount is 1-2 ml / 80 cm 2 . 16h; The drop mechanism comprises a drop pipe (18) suspended above the sample (2), the drop mechanism comprises a plurality of top atomizing nozzles (10) distributed around the drop pipe (18), the sample (2) is processed into a conical surface structure with a convex middle part, the middle part of the sample (2) is an experimental area (201), and the edge is an evaporation area (202). The water outlets of the top atomizing nozzles (10) and the drop pipe (18) are located above the experimental area (201).

2. A salt spray, evaporative corrosion testing apparatus for simulating the hot-dip galvanizing coating in a marine atmospheric environment according to claim 1, characterized by, It comprises a test box (1), an atomization mechanism, a drop mechanism and a sample heating mechanism arranged in the test box (1); The sample heating mechanism is used for supporting and heating the sample (2) to be corroded; The drop mechanism comprises a drop pipe (18) suspended above the sample (2), the upper end of the drop pipe (18) extends out of the test box (1) and communicates with an external cooling water tank (16), and a water flow control valve (17) is arranged on the drop pipe (18); The atomization mechanism comprises a total liquid pipe (9), a top liquid pipe (11) and a top atomizing nozzle (10) arranged on the top liquid pipe (11), the two ends of the total liquid pipe (9) are respectively communicated with the top liquid pipe (11) and a salt solution tank (8) outside the test box (1), and a plurality of top atomizing nozzles (10) are distributed around the drop pipe (18).

3. The salt spray and evaporation corrosion test device for hot-dip galvanizing coating in a simulated marine atmospheric environment according to claim 2, characterized in that, The included angle between the conical surface of the sample (2) and the bottom surface is 3-10 degrees.

4. The salt spray and evaporation corrosion test device for hot-dip galvanizing coating in a simulated marine atmospheric environment according to claim 2, characterized in that, The sample heating mechanism comprises an open-top insulation box (6), a folded heating pad (4) is arranged in the insulation box (6), a heat preservation layer is arranged between the heating pad (4) and the insulation box (6), and the sample (2) is located on the heating pad (4).

5. The salt spray and evaporative corrosion testing device for hot-dip galvanizing coating in a simulated marine atmospheric environment according to claim 4, characterized in that, The heat preservation layer is aluminum foil (5).

6. The salt spray and evaporation corrosion test device for hot-dip galvanizing coating in a simulated marine atmospheric environment according to claim 1, characterized in that, The sidewall of the test box (1) is further provided with a fan (22) for blowing air to the surface of the sample (2).

7. The salt spray and evaporative corrosion testing device for hot-dip galvanizing coating in a simulated marine atmospheric environment according to claim 6, wherein The atomization mechanism further comprises a side atomization assembly for spraying salt mist from the side of the sample (2), the side atomization assembly comprises a side liquid pipe (20) surrounding the fan (22) and a side atomizing nozzle circumferentially spaced on the side liquid pipe (20), and the side liquid pipe (20) is communicated with the total liquid pipe (9) for providing salt solution.

Images