This standard gives guidance on the assessment of the possibility of condensation on steel surfaces before coating. This standard is applicable to determining whether the environmental conditions at the construction site are suitable for coating. GB/T 18570.4-2001 Surface preparation of steel before coating - Test for the assessment of surface cleanliness Guidelines for the assessment of the possibility of condensation before coating GB/T18570.4-2001 Standard download decompression password: www.bzxz.net
This standard gives guidance on the assessment of the possibility of condensation on steel surfaces before coating. This standard is applicable to determining whether the environmental conditions at the construction site are suitable for coating.

ICS 25. 220. 10
National Standard of the People's Republic of China
GB/T18570.4—2001
eqv ISO 8502-4: 1993
Surface preparation of steel substrates before application of paints
Tests for the assessment of surface cleanlinessGuidance on the estimation of the prohability ofcondensation prior to paint application2001-12-13 Issued
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
Implementation on 2002-08-01
CB/T18570.4—2001
This standard is compiled based on I508502-4:1993 "Surface preparation of steel before coating - Tests for assessment of surface cleanliness - Part 4: Guidelines for assessment of performance before coating" and is equivalent to this international standard in terms of technical content and writing format. The difference between this standard and IS (8502-4) is that: this standard deletes the "introduction" of ISO8502.4; in Chapter 3 of this standard, 3.1, 3.2, 3.3, 3.4.3.5, 3.6, 3.7, and 3.8 are added; in the first competition of this standard, 4.1.4.2 and 4.3 replace the numbers A), B), and C) in ISO8502-4; in the last sentence of Article 5.2, the accuracy of the dew point calculator is changed from using a commercially available dew point calculator with sufficient accuracy to using a commercially available dew point calculator with an accuracy better than 0.5C. Appendix A of this standard is a prompt appendix.
This standard is proposed by the China Shipbuilding Industry Corporation. This standard is under the jurisdiction of the 11th Institute of China Shipbuilding Industry. The drafting unit of this standard: the First Institute of China Shipbuilding Industry. The main drafter of this standard: Qin Yinhua.
GB/T18570.4-2 001
ISO Foreword
IS() (International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The development of international standards is usually carried out by ISO technical committees. Each member body has the right to participate in the committee if it is interested in the subject of a technical committee. Official or unofficial international organizations associated with ISO may also participate in this work. ISO works closely with the International Electrotechnical Commission (IEC) in all aspects of electrotechnical standardization. The draft international standards adopted by the technical committees are sent to the member groups for voting. At least 75% of the member groups participating in the vote must vote in favor before they can be published as international standards. International standard ISO8502-4 was developed by ISO/TC35/SC12\Technical Committee for Paints and Varnishes, Sub-Technical Committee "Surface Treatment of Steel before Painting".
IS<) 8502, under the general title "Tests for the assessment of surface cleanliness of steel substrates prepared before application of paint", consists of the following substandards: Part 1: Field test for the determination of soluble ferrous corrosion products (technical report) Part 2: Laboratory determination of chlorides on treated surfaces Part 3: Assessment of dust on steel substrates before application of paint (pressure sensitive tape method) Part 4: Guidelines for the assessment of the potential for condensation before application of paint Part 5: Determination of chlorides on steel substrates before application of paint (ion detector tube method) Part 6: Sampling of soluble impurities on surfaces to be coated (I3rc:sle method) Part 7: Sampling of soluble impurities on surfaces to be coated Analysis of oils and fats Field analysis method Part 8: Analysis of free impurities on surfaces to be coated Field analysis method Users should note that the above parts 5 to 8 are unscheduled work topics. It is planned to publish all the parts listed in ". When published, one or more of the topics may be deleted from the work outline, and the remaining parts may be renumbered. Appendix A is a prompt appendix.
1 Scope
National Standard of the People's Republic of China
Surface preparation of steel before coating
Test for assessment of surface cleanliness
Guidelines for assessment of the possibility of condensation before coating Preparation This standard gives the guidance on the assessment of the possibility of condensation on steel substrates before application of paints and related products. This standard is applicable to determining whether the environmental conditions at the application site are suitable for the application of paints. 2 Reference Standards
GB/T 18570. 4-- 2001
eqvIS0 8502.4:1993
The clauses contained in the following standards constitute the clauses of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised. The parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T74081991 Data elements and exchange formats Information exchange date and time representation (egvISO8601:1988) JS04677-1:1985 Determination of relative humidity in conditioned and tested atmospheres Part 1: Inhalation hygrometer method 1S0) 4677-2:1985 Determination of relative humidity in conditioned and tested atmospheres Part 2: Rotational hygrometer method 3 Condensation possibility
3.1 The relative humidity of the air and the temperature of the steel surface are the basis for assessing the possibility of condensation. There is no simple rule to follow. There are many factors that affect the condensation and evaporation of moisture, making the situation complicated. These factors are: thermal conductivity of the structure; solar radiation on the surface; the flow of ambient air around the structure; surface contamination with hygroscopic substances. These influences can sometimes cause local changes in the material surface or prevent local changes in the steel surface. For example, in some places, the steel surface temperature is reduced or tends to decrease due to heat loss, and in some places, the air is quickly saturated due to poor ventilation. Of course, such factors sometimes have opposite effects. Therefore, each test result should be analyzed very carefully. 3.2 Unless otherwise agreed by the parties, the steel surface temperature should generally be at least 3 °C above the dew point when the coating is applied. Other temperature differences may be specified by the coating manufacturer or agreed upon by the parties concerned. NOTE 1 For materials that can tolerate surface moisture, a temperature difference of less than 3 °C is acceptable. 3.3 The probability of dew point is defined as "high" when the difference between the surface temperature and the dew point is or will fall below the required minimum value. Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on December 13, 2001, and implemented on August 1, 2002
GB/T 18570.4 2001
3.4 ​​When the difference between the surface temperature and the dew point is higher than or will be higher than the required minimum value, the possibility of condensation is defined as "low". 3.5 It is very important to judge whether a temperature drop sufficient to cause condensation occurs during the critical period. Table 1 can be used to help make such a judgment. 1 The relationship between the temperature drop required for condensation to occur and the relative humidity, normalized
Temperature drop,
Note: This data is the average value obtained when the air temperature is 035°C. More accurate values ​​for a given temperature can be obtained from Appendix^ (Suggested Appendix).
3.6 When the relative humidity is 85% or higher, because the maximum distance from the dew point is 2.5°C, it should be strictly judged whether the paint can be applied. 3.7 When relative humidity is high (up to 92%, or only 1.3°C from dew point), coating should be considered only when it is certain that the environmental conditions during coating and drying will remain stable or improve. NOTE 2: This period is usually about 6 hours.
3.8 When relative humidity appears to be satisfactory (e.g., 80%, or 3.4°C from dew point), consideration should be given to maintaining environmental conditions for a suitable period of time to ensure that dew does not occur.
NOTE 3.The appropriate time is usually 6 hours.
4 Instruments
The following instruments should be used. Other instruments may be used in addition to those specified, but they should have the same or higher accuracy as the following instruments.
4.1 For air temperature measurement, a mercury thermometer or a digital electronic thermometer can be used with an accuracy of +0.5°C. 4.2 For air condensation measurement, any of the following instruments can be used. 4.2.1 Aspiration hygrometer and rotary hygrometer, with an accuracy of 3%RII. For humidity calculation tables, see TSO4677-1 and ISO4677-2. 4.2.2 Digital electronic hygrometer, the principle is to measure the change in the capacitance of the polymer membrane. The accuracy is =3%RH, and the working range is relative humidity: 0-100%RI. Temperature: -40~80°C. 4.2.3 Digital electronic filter meter, the principle is to measure the change in resistance in the salt bridge. The accuracy is ±2%RH. The working range is relative humidity: 0~～97%RH, temperature: 0--70℃
4.3 For the measurement of surface temperature, a digital electronic thermometer with an accuracy of ±0.5℃ can be used. Note 1: If the magnetic surface thermometer has the required accuracy, a magnetic surface thermometer can also be used. The magnetic surface thermometer should stay on the steel surface for a sufficient time to measure the actual temperature of the steel surface. 5 Operation steps
5.1 Use the instruments specified in 4.1 and 4.2 to measure the air temperature and relative humidity, with an accuracy of 0.5℃. 5-2 Calculate the dew point, which is the logarithmic function of the vapor pressure at the actual temperature. The dew point can be calculated using a table and graph with air temperature and relative humidity, see Appendix A, or a commercially available dew point calculator with an accuracy better than 0.5℃. 5.3 Use the instrument specified in 4.3 to measure the surface temperature of the oxygen steel. Measure at least one point every 10m of the surface. Use the lowest measured temperature when calculating the dew point. Note 5: When selecting the temperature measurement point, the thickness change of the steel and the influence of shadows should be considered. 5.4 Determine the minimum surface temperature required to avoid condensation under the prevailing environmental conditions. 6 Test report
The test report shall include the following contents:
a) The serial number of this standard;
b) Test date, as specified in GB/T7408;2
c) Instrument used;
d) Dew point;
e) Steel surface temperature:
f) Difference between steel surface temperature and dew point;
g) Minimum temperature difference required to avoid condensation: GB/T 18570. 4—2001
h) Whether the avoidance possibility is assessed as "high" or "low"3
GB/T 18570. 4 --2001
(Appendix to the suggestion)
Dew point determination table
A1 Table A1 gives the dew point temperature corresponding to air temperature and relative humidity. When using Table A1, please pay attention to the following points: a) For each row of relative humidity values, find the higher and lower values ​​close to the actual measured relative humidity values. b) For each row of air temperature values, find the higher and lower values ​​close to the actual measured air temperature values. c) Find the corresponding four dew point temperatures. Perform linear interpolation in two steps and round to 0.1. The values ​​in Table A1 can be obtained by Formula (A1) is used for calculation and is valid at (0'C. (234.175+t)(1no.01+lng)+17.08085t=234.175×
234.175×17.08085=（234.175+z)(ln0.0=1ng)（Al）
Note: From formula (A1) it can be seen that ·ta is a relatively simple function of two variables! and Φ. Therefore, this function is suitable for calculation with a scientific programmable calculator. Such a calculator (including its program) is regarded as the same as Table A. It is superior to Table A1 in that it gives a direct reading of the dew point temperature without interpolation. In addition, a training calculator is usually more convenient to operate in the field than to carry around a large A4-sized calculator. To ensure that the calculator has the correct program, enter the values ​​and values ​​from Table A1 in pairs and compare the results with the corresponding values ​​in Table A1. Relative Dew Point
— 22. 1
. 301, 8
GB/T 18570. 4—2001
Air Temperature t.℃
-12, 4
. 6. h
Relative Dew Point
GB/T 18570.4—2001
Table A1 (continued)
Air Temperature t,bZxz.net
. 5. 4
Relative condensation history
GB/T 18570.4—2001
Table A1 (continued)
Air temperature t, r
Relative humidity
- 13, E
..- 5.
— 36. 4
--- 18. 2
—6, 3
—21,1
—5, 1
GB/T 18570. 4--2001
Table A1 (continued)
Air temperature t, C
——28, 0
— 19. 0
— 17. 8
— 12. 1
-12, 1
..1c. 5
— 12. 5
Relative humidity
GB/T 18570.42001
Table A1 (continued)
Air temperature175×
234.175×17.08085=（234.175+z)(ln0.0=1ng)（Al）
Note: From formula (A1), it can be seen that ·ta is a relatively simple function of two variables ! and Φ. Therefore, this function is suitable for calculation with a scientific programmable calculator. This calculator (including its program) is considered to be equivalent to Table A. It is superior to Table A1 in that it has a direct dew point temperature reading without interpolation. In addition, a training type calculator is usually more convenient to operate in the field than to carry a large A4 size machine. In order to ensure that the calculator has the correct program, the ! and values ​​of Table A1 can be entered in pairs and the results can be compared with the corresponding values ​​in Table A1. Relative humidity
— 22. 1
. 301, 8
GB/T 18570. 4—2001
Air temperature t.℃
-12, 4
. 6. h
Relative humidity
GB/T 18570.4—2001
Table A1 (continued)
Air temperature t,
. 5. 4
Relative condensation
GB/T 18570.4—2001
Table A1 (continued)
Air temperature t, r
Relative humidity
- 13, E
..- 5.
— 36. 4
--- 18. 2
—6, 3
—21,1
—5, 1
GB/T 18570. 4--2001
Table Al (continued)
Air temperature t, C
——28, 0
— 19. 0
— 17. 8
— 12. 1
-12, 1
..1c. 5
— 12. 5
Relative humidity
GB/T 18570.42001
Table A1 (continued)
Air temperature175×
234.175×17.08085=（234.175+z)(ln0.0=1ng)（Al）
Note: From formula (A1), it can be seen that ·ta is a relatively simple function of two variables ! and Φ. Therefore, this function is suitable for calculation with a scientific programmable calculator. This calculator (including its program) is considered to be equivalent to Table A. It is superior to Table A1 in that it has a direct dew point temperature reading without interpolation. In addition, a training type calculator is usually more convenient to operate in the field than to carry a large A4 size machine. In order to ensure that the calculator has the correct program, the ! and values ​​of Table A1 can be entered in pairs and the results can be compared with the corresponding values ​​in Table A1. Relative humidity
— 22. 1
. 301, 8
GB/T 18570. 4—2001
Air temperature t.℃
-12, 4
. 6. h
Relative humidity
GB/T 18570.4—2001
Table A1 (continued)
Air temperature t,
. 5. 4
Relative condensation
GB/T 18570.4—2001
Table A1 (continued)
Air temperature t, r
Relative humidity
- 13, E
..- 5.
— 36. 4
--- 18. 2
—6, 3
—21,1
—5, 1
GB/T 18570. 4--2001
Table Al (continued)
Air temperature t, C
——28, 0
— 19. 0
— 17. 8
— 12. 1
-12, 1
..1c. 5
— 12. 5
Relative humidity
GB/T 18570.42001
Table A1 (continued)
Air temperature
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