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The method of calculating the pitting potential of stainless steel in cooling water and waste water

A technology of pitting potential and stainless steel, which is applied in weather resistance/light resistance/corrosion resistance, measuring devices, instruments, etc., and can solve problems such as heavy workload

Active Publication Date: 2017-01-25
SHANGHAI UNIVERSITY OF ELECTRIC POWER
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In addition, the effect of temperature on pitting potential E b The impact of can not be ignored, so before E b can only be obtained by experiment
If there is a water quality component, a group of tests should be done; if the water quality component is the same, but the temperature is different, the test should be done, and the workload of the test is very heavy.

Method used

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  • The method of calculating the pitting potential of stainless steel in cooling water and waste water
  • The method of calculating the pitting potential of stainless steel in cooling water and waste water
  • The method of calculating the pitting potential of stainless steel in cooling water and waste water

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Effect test

example 1

[0074] Example 1: Cl in waste water - , SO 4 2- 、HCO 3 - and NO 3 - The content of each is 6 Hmmol·L -1 , 4 Hmmol L -1 , 2Hmmol L -1 and 0.3 Hmmol•L -1 , pH value = 8.3, find the pitting potential of 304 stainless steel in the cooling water when the working temperature is 40, 50 and 46 °C respectively.

[0075] Solution: NO 3 - Concentration≤0.6mmol·L -1 negligible, equivalent to SO 4 2- Concentration = 4+2 = 6 Hmmol•L -1 . Use relational formula (2) and (3) to obtain the pitting potential y of 304 stainless steel at the working temperature of 40 and 50 °C 40 and y 50 They are:

[0076] the y 40 = 4.929×6 2 -0.638×6 2 -107.72×6+75.58×6-3.924×6×6+784.77=605 mV

[0077] the y 50 = 587mV

[0078] Calculate pitting potential y at 46°C by linear interpolation method 46 = 587+(605-587)×6 / 10=597.8 mV

[0079] Therefore: when the working temperature is 40, 50 and 46 °C, the pitting potentials of 304 stainless steel in the waste water are 605, 587 and 597.8 mV...

example 2

[0080] Example 2: Cl in cooling water - , SO 4 2- 、HCO 3 - and NO 3 - The content of each is 8 Hmmol·L -1 , 5 Hmmol L -1 , 2Hmmol L -1 and 0.4 Hmmol•L -1 , pH value = 7.8, find the pitting potential of 304 stainless steel in the cooling water when the working temperature is 30, 40 and 35 °C respectively.

[0081] Solution: NO 3 - Concentration≤0.6mmol·L -1 negligible, equivalent to SO 4 2- Concentration=5+2=7 Hmmol•L -1 . Using relational formulas (1) and (2), the pitting potentials of 304 stainless steel at operating temperatures of 30 and 40°C are 548 and 517mV respectively, and the pitting potential y at 35°C can be obtained by linear interpolation 35

[0082] the y 35 = (548+517) / 2=532.5 mV

[0083] Therefore: when the working temperatures are 30, 40 and 35 °C, the pitting potentials of 304 stainless steel in the cooling water are 548, 517 and 532.5 mV respectively

[0084] The above relational formulas (1), (2) and (3) are also applicable to the compos...

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Abstract

The invention discloses a method for obtaining the pitting potential of stainless steel in different cooling water and waste-heat water. The method is characterized by starting from an actual water sample, finding five major components affecting the pitting potential of stainless steel from infinite water quality components, ignoring two major components and merging other two major components according to the functions and the concentration conditions in most water, and then considering the influence of temperature by an interpolation method, so that a 6-element nonlinear relation is changed into a 2-element nonlinear relation, and the relation of the pitting potential of stainless steel can be fit through a few tests while the data distribution is uniform, the significance is high and the error is little; the pitting potential of the stainless steel in different conditions of water quality components and temperature can be calculated by use of the relations according to the major water quality components and working temperature, thereby greatly reducing the workload of tests; and the method is suitable for most cooling water and waste-heat water in which the stainless steel can be used.

Description

technical field [0001] The invention relates to a method for calculating and obtaining the pitting potential of stainless steel in different cooling water and residual hot water. Background technique [0002] The main failure form of stainless steel in cooling water and waste water is pitting corrosion. Patent ZL 03115581.2 has announced the criterion for judging whether pitting corrosion will occur in stainless steel in cooling water. pitting potential E b Compared with a specific potential value Es as a criterion to determine whether the stainless steel pipe material will undergo pitting corrosion in the cooling water, if E b ≥ Es, it is considered that the stainless steel pipe of this type will not undergo pitting corrosion in this cooling water. The value range of Es is ±2[00mV, is the oxygen evolution equilibrium potential of the cooling water, which can be obtained by calculation. Although someone has fitted the relationship between the pitting potential of cer...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N17/02
Inventor 梁磊张建良赵阳刘世宏
Owner SHANGHAI UNIVERSITY OF ELECTRIC POWER
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