Research on the Construction Technology of Inorganic Zinc-Rich Paint Used in Nuclear Power Plant

introduction

Nuclear power plants are mostly located in coastal areas, and the corrosion protection requirements for steel containment are relatively high.

This paper mainly conducts experimental simulations on various working conditions of nuclear power plant construction, investigates the influence of construction technology and maintenance technology on the performance of inorganic zinc-rich coatings, and provides data support for subsequent formulation of inorganic zinc-rich coating construction specifications based on the test results.

Experiment content

The contents of this part of the experiment were carried out from the construction links of paint spraying, curing, curing degree inspection and coating surface treatment to conduct process simulation tests.

1 Use different spraying equipment to spray the test board

A high-pressure airless spray gun and an air spray gun were used to spray the inorganic zinc-rich paint test panels.

2 Simulation experiment of paint film curing effect over time

Taking into account the complex construction environment of the construction site and the large size of the spraying equipment, the humidification and maintenance of the inorganic zinc paint film cannot achieve 100% coverage.

3 Comparison experiment of MEK wiping effect with different reagents

Carry out the inorganic zinc-rich primer sample spraying, the sprayed samples are sprayed with different degrees of water mist curing, respectively using methyl ethyl ketone, acetone, mixed thinner (50% isopropanol + 35% propylene glycol methyl ether + 15% ethanol) , Methyl isobutyl ketone was wiped with MEK, and the wipe results were compared and analyzed.

4 Experiment on the influence of paint film surface polishing on coating performance

Carry out the inorganic zinc-rich primer sample spraying, the coating thickness is 160~250μm, after spraying, at different time points (1h, 2h, 24h, 48h, after fully curing), the film thickness will be polished and thinned by 30-60μm; MEK before polishing Test, perform MEK and adhesion test after the paint film is fully cured.

5 Experiment on the influence of overcoating on coating performance

Carry out the inorganic zinc-rich primer sample spraying.

Experimental results and analysis

1 The influence of spraying pressure on coating performance

MEK wipe and adhesion test were performed on the inorganic zinc coating test board (1-2#) using air spraying and the inorganic zinc coating test board (3-4#) using high pressure airless spraying respectively.
The test results are shown in Table 1.
Shown.

Table 1 MEK and adhesion test results of different spraying methods

Figure 1 The micro-morphology of the coating surface of different spraying methods

It can be seen from Table 1 that both high-pressure airless spraying and air spraying can be used to coat MEK up to the highest level 5, in terms of adhesion value, high-pressure airless spraying is significantly greater than air spraying; using a 100x magnifying glass Observing the surface of the paint film of the two spraying methods (Figure 1), it can be clearly seen that the surface of the air spraying paint film is rough and there are more particles, and the surface of the high-pressure airless spraying paint film is relatively flat and smooth.

According to the characteristics of inorganic zinc-rich paint, its dry film zinc content exceeds 85%.
In order to resist sag, the formula is designed with a fast-drying solvent system.
Therefore, when spraying with air with a lower pressure, dry spraying is prone to occur, that is, partial The solvent evaporates before it reaches the surface of the sprayed substrate, which will eventually cause the paint film structure to be loose and the surface rough, so the adhesion value is low.
Therefore, in the paint construction, try to use high-pressure airless spraying, which is conducive to improving the adhesion of the coating and the appearance of the paint film.

2 The curing effect of the paint film changes with time

Table 2 shows the results of MEK and adhesion tests performed regularly on the indoor and outdoor test panels.
The MEK wipe of the test board placed indoors for 7 to 15 days can reach level 5, and the adhesion test value of 30d is close to the maximum value, indicating that the paint film is nearly fully cured after being placed for 30 days; the MEK wipe of the test board placed outdoors can reach level 5, with Focusing on the test value for 15d is close to the maximum value, indicating that the paint film is almost completely cured after being placed for 15d.
The experimental results show that the inorganic zinc paint film can be completely cured without artificial humidification and curing, but the curing time is longer, and the curing time is more than 1 month when placed indoors.
In order to shorten the construction period and improve the curing effect of the paint film, it is recommended to artificially humidify and maintain the coating during construction.

Table 2 Experimental results of the curing effect of the paint film over time

3 Comparison of MEK wiping effects with different reagents

MEK，，，，MEK。，MEK，、、MEK，MEK。

2 MEK

3 MEK

2，1#10#，、、、4；3 4MEK，4。，（50%+35%+15%）。

4

、MEK。（3），MEK5。，，；，。，，100（4），，。，，。

3 MEK

4

5

The content of this experiment is mainly aimed at the simulation verification of the operation of overcoating the construction area where the coating thickness does not meet the requirements to reach the specified thickness during the construction process, and inspecting whether the paint film performance meets the requirements.
According to the experimental data (Table 4), the adhesion of the inorganic zinc coating decreased to varying degrees after overcoating.
After 0.
5h, the adhesion of the overcoating decreased by about 20%; when the overcoating interval exceeded 12h, the adhesion of the coating The focus value has dropped by more than 50%, and the coated MEK wipe cannot reach level 5.
Use a 100x magnifying glass to observe the surface of the paint film before and after the overcoating (Figure 5).
The surface of the uncoated paint film is relatively flat and smooth.
After 12h and 24h, the surface of the overcoated paint film is rough and uneven, indicating inorganic zinc.
Dry spraying occurred during paint spraying.
Therefore, based on the analysis of the above results, the performance of the paint film has declined after the overcoating of the inorganic zinc coating.

Table 4 Coating performance test results before and after overcoating

Figure 5 The micro morphology of the coating surface before and after overcoating

Conclusion

(1) Inorganic zinc paint adopts high-pressure airless spraying, and the coating adhesion and paint film appearance are obviously better than air spraying;

(2) The inorganic zinc coating can be completely cured without artificial humidification and curing, but the curing time is longer, and it takes more than 1 month for the paint film to fully cure when placed indoors;

(3) The MEK wiping effect of methyl isobutyl ketone and mixed thinner (50% isopropanol + 35% propylene glycol methyl ether + 15% ethanol) on inorganic zinc coating is equivalent to methyl ethyl ketone and acetone.
When it is difficult to obtain, the former two can be used as MEK wiping reagents for inorganic zinc coatings;

(4) Polish the inorganic zinc paint film after it is fully cured, and there is no significant difference between the adhesion of the coating after polishing and the adhesion of the unpolished coating.
If the uncured paint film is polished, the coating adhesion value is obviously low;

(5) Compared with the uncoated coating, the various properties of the paint film after the inorganic zinc coating have been overcoated.
When the overcoating interval exceeds 12h, the adhesion value of the coating drops by more than 50%, and the coating Layer MEK wipes can't reach level 5.

References (omitted)

Authors | Guo Liangliang1, Liu Xiaoqiang2, Zhu Yajun1, etc.

(1.
CNOOC Changzhou Coating Chemical Research Institute Co.
, Ltd.
; 2.
Shanghai Nuclear Engineering Research and Design Institute Co.
, Ltd.
)