Source: material protection 1999
1
Corrosion science is an applied science closely related to national economy and national defense construction. Judging from its subject characteristics, it is also an interdisciplinary subject that intersects with many related disciplines such as chemistry (electrochemistry), physics, mechanics, metallurgy and microbiology, and has many similarities with environmental science in many aspects. Technically, with the continuous development of optics, electron optics and surface science and technology, the development of corrosion science and protection technology has been promoted. This paper will discuss several noteworthy development trends of corrosion science and protection technology in recent years.
2 development trend
2. In-situ study on the interface reaction of1metal/corrosive medium.
Based on the latest achievements of EIS, AFM, STM, SERS and QCM, the process and rapid steps of metal surface reaction at the interface between metal and corrosive environment media are comprehensively studied in situ, especially in the research of corrosion processes such as corrosion electrochemistry, high temperature oxidation/corrosion wear and thermal corrosion, stress corrosion cracking, corrosion fatigue and hydrogen corrosion, which has attracted extensive attention.
For example, in recent years, the State Key Laboratory of Metal Corrosion and Protection and the Royal Swedish Institute of Technology have carried out extensive cooperative research in this field, and achieved many research results in the atmospheric corrosion mechanism of metals under thin electrolyte films.
2.2 Reliability of Structure in Corrosive Environment
With the development of industry, more and more large-scale industrial devices/equipment operate under harsh and intensified working conditions such as high temperature, high pressure, high load stress, high heat flow/high quality flow/multiphase flow and strong corrosive environment.
The corrosion damage under the synergistic action of the above factors largely determines the reliability of industrial devices/equipment in use. Therefore, the theme of the international corrosion conference held in Houston, USA, "Corrosion control aimed at ensuring its reliability under low investment conditions" and the international conferences held in Cambridge, England and Honolulu, USA, "Life prediction of structures in corrosive environment" all show that the reliability of industrial devices/equipment has become a hot issue of concern.
There are countless examples that the reliability of industrial equipment is decisively restricted by corrosion damage, and the reliability of military equipment is also generally restricted by corrosion damage, which directly affects or even loses its combat capability. For example, in 1990, the electronic equipment of the US Air Force failed due to corrosion, accounting for 20% of its total. In the same year, the global maintenance cost of corrosion-related electronic equipment reached 50× 108 USD, and this figure will increase day by day [1]. The corrosion of air force electronic equipment is still the same in the best working environment, and the severity of corrosion of industrial equipment in worse environmental conditions can be imagined.
In fact, when the pollutants in the atmosphere are far below the requirements of environmental protection, electronic equipment will be corroded and destroyed. For example, the upper limits of sulfur dioxide and hydrogen sulfide in the atmosphere stipulated by environmental protection are 1 000× 10-9 and 10 000× 10-9 respectively, while the upper limits of safe concentrations of sulfur dioxide and hydrogen sulfide that do not corrode electronic equipment are only 30×10 respectively. Ensuring the normal operation of electronic equipment requires environmental corrosiveness, even far exceeding the requirements of ensuring human health.
2.3 On-line detection/evaluation of equipment corrosion/maintenance
In order to find out the corrosion damage in time, especially the hidden danger of malignant corrosion damage accidents that cause huge economic losses and serious social consequences, it is the key to ensure the operation reliability of large-scale industrial devices/equipment under harsh and dense working conditions to carry out online, real-time and nondestructive detection/evaluation and corrosion prediction, and on this basis, timely maintenance of industrial devices/equipment. In the past 10 years, in order to meet this demand, the laboratory led by the author has developed and continues to develop a series of online, real-time, nondestructive detection/evaluation and prediction technologies for corrosion.
According to the statistics of the whole world, the offshore operation expenses account for 20% of the offshore oil and gas development expenses. The annual growth rate of this figure is 1 1%, and 30% of the offshore operation cost is used to pay for inspection/repair/maintenance (IRM) mainly against corrosion damage [4]. This statistic shows that IRM plays an important role in the technical economy and safety guarantee of production.
2.4 a new method of material optimization-LCC [5]
A new material selection method-the total cost analysis of industrial devices/equipment in the service life. LCC(Life cycle costs) is different from the traditional material selection method. LCC considers all the costs of devices/equipment in the whole service life until it is completely updated. Including material procurement, freight, construction and installation, operation, maintenance, shutdown, wear and replacement of wearing parts and their residual value, the latter mainly considers the initial investment mainly based on material acquisition cost.
LCC can be calculated by the following formula:
Where AC—— refers to the cost of material procurement, including material procurement and freight.
IC- building installation fee
CJ-operating expenses in the first year, including production, shutdown and maintenance expenses.
Rj- the replacement cost of the I-th unavailable system
R- real interest rate,% divided by 100.
A—— Replacement times in the whole life cycle.
N—— The number of life cycles of equipment installation in a given year.
From some examples cited in table 1 ~ 3 [6], it can be clearly seen that the cost of equipment built with high-grade corrosion-resistant alloy is only several times or even nearly 10 times more expensive than that built with low-grade carbon steel or low-alloy steel, but the construction and installation costs are close. The former is basically maintenance-free equipment and does not need to spend a lot of follow-up expenses. The other expenses listed above are often higher than the initial investment savings.
Table 1 LCC calculation of shell-and-tube condenser in refinery (complete corrosion of carbon steel)
Material cs 316l saf2304 saf2205 saf2507.
The cost of each condenser tube is 1.0 6.5 5.5 7.0 9.5.
The structure and installation cost of each condenser pipe is 3.0 3.5 3.5 3.5 4.0.
The total installation cost is 4.010.09.010.513.5.
Life (room temperature) 10 month > 5 years > 5 years > 5 years > 5 years > 5 years > 5 years > 5 years.
Cl-, Cl-, 150℃ < 10+00 months < 1 year > 5 years > 5 years > 5 years.
Cl-, 180℃ < 10 month < 1 year < 1 year > 5 years > 5 years.
Cl-, 300℃ < 10 month < 1 year < 1 year > 5 years.
Change the quantity every five years, and there is no Cl-6.0 <1.0 <1.0 <1.0 <1.0.
Change the quantity every five years, including Cl-(SCC) 6.0 5.0 < 1.0.
t< 150 ℃ < 1.0
t< 180 ℃ < 1.0
t