Corrosion resistant and high pressure resistant!

Epoxy resin is widely used in the field of anti-corrosion of metal materials due to its good adhesion to metal substrates, acid and alkali resistance, and excellent temperature resistance

Amorphous polymers have a glass transition temperature

1 Preparation of high temperature resistant epoxy powder coating and modification of epoxy resin

1.

The epoxy powder coating composition comprising: an epoxy resin, curing agent, fillers, leveling agents and the like

Figure 1 Preparation process of epoxy powder coating

Among them, epoxy resin and curing agent can affect the glass transition temperature of the coating, but epoxy resin has a greater impact

Figure 2 Structural formula of bisphenol A epoxy resin

From the structural formula of bisphenol A epoxy resin in Figure 2, it can be seen that the cross-linking reaction groups of the resin are only located at the two ends of the molecular formula, and the molecular functionality is 2, the coating density after curing and cross-linking is relatively low, and the cured glass The melting temperature is basically around 100°C

1.

In recent years, people have done a lot of work on the modification of epoxy resin

Figure 3 o-cresol novolac epoxy resin

Figure 4 Phenolic novolac epoxy resin (EPN)

Figure 5 Bisphenol A novolac epoxy resin

US patents US9169417[6] and US8937114[7] respectively introduced an epoxy powder coating containing divinylarene dioxide and an epoxy resin containing bisphenol naphthenic compounds.

Of course, simply increasing the Tg value of the coating cannot be used as a real product.

2 Application of high temperature resistant epoxy powder coating in the field of petroleum exploitation

2.

Drill pipes, tubing and casing used in the process of oil extraction

As the underground depth increases, the temperature and pressure will increase accordingly.

2.
2 Quality evaluation of high temperature epoxy powder coating

For the quality control of epoxy powder coatings with high glass transition temperature, there is currently no clear technical standard as a basis
.
At present, our country can only refer to the two standards mentioned above in this work
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However, the underground environment has the characteristics of complexity and aggressiveness, and the prediction of the protective ability of the coating and the service life of the coating is a problem that the industry is very concerned about
.
Now the research departments of various countries or major companies have also conducted research on this work
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The high temperature and high pressure test of the coating is a relatively direct test method for the performance of the reactive coating.
Researchers agree that the "JO Wafra" test condition [9] is the most demanding high temperature and high pressure test, and the conditions are listed in Table 3.

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After the test, the coating has no blistering, no swelling, and good adhesion to the substrate as the criterion
.

In addition, extending the test time of high temperature and high pressure can effectively evaluate the performance of the coating
.
Some researchers have proposed to extend the high temperature and high pressure test time to 60 days.
In theory, the longer the high temperature and high pressure test time, the stronger the reliability of the measured results
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However, this method takes a long time to test, and the test cost is very high
.
According to Traylor [10] statistics, the test cost is shown in Table 4
.

It can be seen from the data in Table 4 that 60 days of high temperature and high pressure testing requires a cost of 25,000 US dollars
.
In China, the cost of high temperature and high pressure testing is also very high.
The cost of high temperature and high pressure testing for 24 hours is about 30,000 yuan
.
Time and cost are issues that have to be considered.
Therefore, R&D personnel in various countries are also actively seeking good evaluation measures to effectively test and evaluate the quality of high Tg epoxy powder coatings
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Traylor [10] reported a fast and economical method for testing the corrosion resistance of coatings
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According to field experience and laboratory research, a high protective coating with good barrier properties has high electrical resistance
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Therefore, the electrochemical impedance (EIS) method was used to test the corrosion resistance of the coating with high glass transition temperature, and it was found that the LogZ value was in the range of 9-11.
It is believed that the coating has excellent corrosion resistance
.

3 The development trend of high temperature epoxy powder coatings

Epoxy powder coatings have been used for more than 60 years in the field of anti-corrosion, especially in the field of heavy-duty anti-corrosion.
The pipelines laid 60 years ago are still in service, indicating the excellent corrosion resistance of epoxy coatings
.
High temperature resistant epoxy powder coatings combine the advantages of epoxy powder coatings with high adhesion to metal substrates, high acid and alkali resistance, and high temperature resistance
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At the same time, with the continuous improvement of market demand and technical level, the demand for high temperature resistant epoxy powder coatings will become greater and the scope of application will become wider and wider
.
Not only in the fields of oil exploration and exploration, but also in other fields, the application of internal and external anti-corrosion of high-temperature medium transportation pipelines is also increasing
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The quality control methods for high-temperature epoxy powder coatings will also become more scientific and reasonable .