CN-121978248-A - Method for measuring moisture content of anticorrosive paint based on gas chromatography

CN121978248ACN 121978248 ACN121978248 ACN 121978248ACN-121978248-A

Abstract

The application provides a method for measuring the moisture content of an anticorrosive paint based on a gas chromatography, which comprises the steps of carrying out gradient dilution and volume fixing on water by a dilution solvent to obtain a plurality of standard solutions, carrying out gradient dilution and volume fixing on an internal standard substance by the dilution solvent to obtain an internal standard solution, placing different volumes of standard solutions in a volumetric flask, adding quantitative internal standard solutions, supplementing the dilution solvent to a target volume to obtain a plurality of groups of working solutions, carrying out gas chromatography detection on each group of working solutions by a single-point relative response factor test method to obtain the peak area of water, the peak area of the internal standard substance and the relative response factor of water, constructing a plurality of candidate functions based on a preset function by taking the ratio of the peak area as an abscissa and the relative response factor as an ordinate to obtain a fitting curve expression, calculating the fitting degree of each candidate function, selecting the highest fitting degree as a target function, measuring a sample to be measured to obtain target data, and substituting the target function to obtain the moisture content. The determination method improves the accuracy of the moisture content test result.

Inventors

GAO LIN
FU JINYING
DONG NA
DONG TAO
WANG GUOJUN
BAI XU

Assignees

沈阳盛达惠发化工有限公司

Dates

Publication Date: 20260505
Application Date: 20260309

Claims (10)

1. A method for determining the moisture content of an anticorrosive paint based on gas chromatography, which is characterized by comprising the following steps: carrying out gradient dilution on water by using a dilution solvent, and fixing the volume to a set volume to obtain a plurality of standard solutions; performing gradient dilution on the internal standard substance by using a dilution solvent, and fixing the volume to a set volume to obtain an internal standard solution; Respectively taking all standard solutions with different volumes, placing the standard solutions into a volumetric flask, correspondingly adding quantitative internal standard solutions, supplementing the diluting solvent to a target volume according to preset requirements, and uniformly mixing to obtain a plurality of groups of working solutions; The single-point relative response factor test method is adopted to carry out gas chromatography detection on a plurality of groups of working solutions respectively, and the peak area of water in each group of working solutions is obtained Peak area of internal standard And a relative response factor R of water; constructing a plurality of candidate functions based on a preset function by taking the peak area ratio of water corresponding to each group of working solution and an internal standard as an abscissa and the relative response factor R of the corresponding water as an ordinate, so as to obtain a fitting curve expression of each candidate function; based on abscissa data of each working solution, calculating the fitting goodness of each candidate function fitting curve expression respectively, and determining a candidate function corresponding to the highest value in the fitting goodness as an objective function; And measuring the sample to be measured to obtain target data, and substituting the target data into the target function to obtain the moisture content of the sample to be measured.
2. The method for determining the moisture content of the anti-corrosive paint based on the gas chromatography according to claim 1, wherein the preset function form comprises a quadratic function and a logarithmic function.
3. The method for determining the moisture content of the anticorrosive paint based on the gas chromatography according to claim 2, wherein the internal standard is isopropanol and the diluting solvent is N, N-dimethylformamide.
4. A method for determining the moisture content of a gas chromatography-based anticorrosive paint according to claim 3, wherein when the objective function is a quadratic function, the functional expression is r=a (peak area of water/peak area of isopropyl alcohol) 2 +b (peak area of water/peak area of isopropyl alcohol) +c; when the objective function is a logarithmic function, the functional expression is r= aln (peak area of water/peak area of isopropanol) +b, where a, b, c are constants.
5. The method for determining the moisture content of the anticorrosive paint based on the gas chromatography according to claim 4, wherein the step of determining the sample to be tested to obtain target data, and substituting the target data into the target function to obtain the moisture content of the sample to be tested comprises: Measuring a sample to be measured to obtain target data, wherein the target data comprises peak areas of water and isopropanol; Substituting the target data into the target function to determine a first relative response factor; Calculating the moisture content of the sample to be measured based on a first formula, wherein the first formula is as follows: ; for the moisture content in the sample, 、 Is the mass of isopropanol and the mass of the sample to be measured, 、、 The peak area of isopropanol, the peak area of water in a sample to be detected and the peak area of water in a blank sample are shown, and R is a first relative response factor.
6. The method for determining the moisture content of the anticorrosive paint based on the gas chromatography according to claim 5, wherein determining the candidate function corresponding to the highest value in the goodness of fit as the objective function comprises: Comparing the highest value of the fitting goodness with a preset goodness value; when the highest value of the fitting goodness is larger than or equal to a preset goodness value, determining a candidate function corresponding to the highest value in the fitting goodness as an objective function; And when the highest value of the fitting goodness is smaller than the preset goodness value, adjusting the sampling amount of the water in the standard solution, and re-measuring the relative response factor of the water in the standard solution.
7. The method for determining the moisture content of a gas chromatography-based anticorrosive paint according to claim 6, further comprising: substituting target data into an objective function to obtain a first relative response factor R multiplied by a second relative response factor R, and correcting the first relative response factor R; Wherein, if the objective function is a quadratic function, after R is calculated, the verification is performed - )/ Whether the ratio of (2) is 0.01-0.4; If the horizontal coordinate range is exceeded, then - )/ When >0.4, the corrected first relative response factor value is Rx 0.98, when% - )/ When <0.01, the corrected first relative response factor value is corrected to Rx 1.02; The modified Rx is used in a first formula to calculate the moisture content to compensate for systematic errors in the edge region of the fitted curve.
8. The method for determining the moisture content of a gas chromatography-based anticorrosive paint according to claim 7, further comprising: Calculating the corrected ratio Y of the peak area of water and an internal standard substance of a sample to be detected, wherein Y= =% - )/ ; If Y is less than or equal to 0, judging that blank deduction is abnormal or the moisture content of the sample is lower than the detection lower limit, and re-detecting after re-preparing the blank sample and the sample to be detected; if 0 < Y < 0.02, R is corrected to Rx (1+0.03Xln (0.02/X)), X is the water peak area/isopropyl alcohol peak area.
9. The method for determining the moisture content of a gas chromatography-based anticorrosive paint according to claim 1, further comprising: peak area of water in sample to be measured <2× When the water content is judged to be lower than the detection lower limit, wherein the detection lower limit is 0.1%; when the peak area of isopropanol When the deviation of the area average value of the isopropyl alcohol peak in the detection of the standard solution exceeds +/-10%, judging that the response of the instrument is abnormal, and re-calibrating the temperature of the sample inlet of the gas chromatograph and the flow rate of the carrier gas and then re-detecting; when (a ] - ) And if the sample is negative, judging that blank deduction is abnormal, and detecting after preparing the blank sample and the sample to be detected again.
10. The method for measuring the moisture content of the anti-corrosive paint based on the gas chromatography according to claim 1, wherein, If the fitting goodness R 2 of a plurality of candidate functions is more than or equal to 0.96, the objective function selection principle is that the priority of the quadratic polynomial function is higher than that of the logarithmic function by comparing the residual square with the combined function complexity screening.

Description

Method for measuring moisture content of anticorrosive paint based on gas chromatography Technical Field The application relates to the technical field of moisture measurement, in particular to a method for measuring the moisture content of an anticorrosive paint based on gas chromatography. Background As an economic and efficient protection means, the anticorrosive paint has the core materials for prolonging the service life of the base material and ensuring the safe and stable operation of engineering by forming a continuous and compact protective film on the surface of the base material to prevent the corrosive medium from contacting the base material or playing a protection role by mechanisms such as cathodic protection, corrosion inhibition and the like. According to film forming materials, anti-corrosion mechanisms and application scenes, the anti-corrosion coating can be divided into a plurality of categories and form a composite protection system. The epoxy resin coating has strong adhesive force and excellent chemical corrosion resistance, accounts for more than 40% of the market share of the global anti-corrosion coating, is widely applied to scenes such as ship cabins, oil gas storage tanks, pipelines and the like, has good flexibility and weather resistance, is mostly applied to parts such as ship decks, ocean platform outer layers and the like which need to be attractive and protected, realizes long-term protection through a cathode protection mechanism by zinc-based coating (zinc content is generally more than 80%), is suitable for severe scenes such as ocean steel structures, nuclear power containers and the like, and is gradually popularized in the high-end anti-corrosion field by virtue of the characteristics of super weather resistance, low VOC, self-healing and the like. In practical application, a multi-layer composite system of primer, middle layer and finish paint is often adopted, such as a zinc-based primer, epoxy middle layer and polyurethane finish paint combination in the field of ships, and the design life can reach 15-20 years. With the development of society, low VOC anticorrosive paint such as waterborne, solvent-free becomes the trend, but no matter be traditional solvent type paint or novel environmental protection coating, moisture is the key negative factor that influences its workability, film quality and protection durability. The sources of the moisture are various, and the moisture not only comprises high humidity in a construction environment, substrate surface condensation (such as 'sweat' of an offshore platform and condensation of a bridge early morning), and residual moisture in the substrate, but also comprises moisture invasion of raw material carrying, storage and transportation links in the coating production process, and rainwater, seawater, industrial wastewater infiltration and the like in the service environment. Although the water exists only in the form of micron-sized water film, the protection effect of the anti-corrosion paint can be damaged in a multi-dimensional way from the physical and chemical aspects, and a series of painting defects and failure problems are caused. There is a need to accurately calculate the moisture content of the anticorrosive paint. Currently, the method for measuring the water content of the anti-corrosion coating in the industrial field mainly comprises two major types of karl fischer method and gas chromatography. The karl fischer method is used as a traditional water determination method, and the water content detection is realized based on the quantitative reaction principle of iodine and water, but the method has strong selectivity to sample types, components such as an organic solvent, a corrosion inhibitor and the like in the anticorrosive paint easily pollute a detection electrode, so that the titration endpoint judgment error is increased, the method has poor parallelism, the relative error is usually more than 5%, and the high-precision detection requirement is difficult to meet. The gas chromatography is a mainstream technology for detecting the water content of the current anticorrosive paint by virtue of the advantages of low instrument configuration requirement, simple and convenient operation, strong sample compatibility and the like, and the core principle of the gas chromatography is that the water content is calculated by separating and detecting the peak areas of water and other components and combining a response factor. However, the conventional gas chromatography has the obvious technical defects that on one hand, a common dilution solvent (such as esters and hydrocarbons) for the anti-corrosion coating is easy to absorb moisture in the air, so that a reagent background moisture interference detection result is caused, on the other hand, the conventional method is insufficient in subtraction logic of blank interference and difficult to accurately offset a systematic error caused by the reagent, on the