Complete Solution of Nickel Tube Selection| N4/N6/N200/Ni201 grade comparison + 5 types of media + 5 steps to avoid pits

Published by Engineering Team, Shaanxi Qianyi Tuoda Technology Co., Ltd on 2026-08-06

Nickel tubes cannot simply be used as a substitute for titanium., In concentrated alkali, high temperature, Organic acids and other specific conditions, Nickel material belongs to special pipe with outstanding adaptability.Shaanxi 100 Billion Tuoda Taking Root in Baoji Titanium Valley of China, Deep cultivation of nickel non-standard products for many years, Contact a large number of pipe selection errors, Titanium materials used in many working conditions will fail quickly, And concentrated sodium hydroxide, high temperature organic acid, Nickel tubes are used for specific chloride media, It can run stably for 5 years without leakage.This article systematically explains N4, Ni201 Nickel tube grade difference, Five types of media adaptation schemes, Mainstream implementation standards and five-step pit avoidance points, Convenient for engineering design and procurement personnel to complete nickel tube selection.

core conclusions, Nickel tube selection to grasp three key points, The first priority is to select the type according to the medium type, Nickel material is suitable for concentrated alkali conditionSecond, pay attention to the use temperature, temperature ≥300℃, choose low carbon grade Ni201;Third, confirm the implementation of standards, distinguish between national standards, ASME, European standards, Japanese standards system.If the grade is not properly selected, the pipeline is prone to stress corrosion cracking within 1 to 3 years.

First, nickel tube four types of brand characteristics detailed explanation

N6 corresponds to UNS number N02200, that is, American standard Ni200, carbon content control within 0.10%, belongs to general pure nickel materials, suitable for concentrated alkali conditions within 300℃;N4 corresponds to UNS number N02201, That is, American standard Ni201, Carbon content ≤0.02%, Low carbon properties can inhibit high temperature embrittlement, Suitable for concentrated alkali above 300℃, high temperature organic acid conditionN200 is N02200, and the American standard Ni200 is the same material, mostly used for export projects;Ni201 is a low carbon grade of American standard, which is consistent with N4 material and is mainly used in high temperature conditions at the outlet.

How to choose between N4 and N6? A: N4 (Ni201) carbon content ≤0.02%, N6 (Ni200) carbon content ≤0.10%.When operating temperature ≥300℃, N4 is required., Graphite precipitates in high carbon materials at high temperatures, Causing embrittlement of materialsOperating temperature ≤300℃ conditions, select N6 can meet the use requirements.

Guidelines for matching working conditions of Class II and V media

Concentrated sodium hydroxide medium with concentration of 30% or more, N6 is preferred within 300 ° C, Temperature above 300℃ N4, The upper limit temperature is about 320℃., Titanium material is easy to brittle crack in concentrated alkali environment, Nickel material has obvious advantages in alkali corrosion resistanceRecommended N4 for high temperature organic acid conditions, Applicable temperature range 200-320℃, Low carbon grades Stable resistance to organic acid corrosionsodium chloride, such chloride media as calcium chloride, N6 shall be selected within 200℃, Good chloride ion pitting resistanceHF medium can be carefully selected N6, Applicable temperature is not higher than 50℃, Nickel has limited resistance to hydrofluoric acidMolten sodium hydroxide medium, temperature 320 to 400℃ scene must choose N4, N6 in this environment will occur embrittlement, can not be used.

III. Five types of common implementation standards

GB/T 2882-2013 Seamless nickel pipe, mostly used for domestic projects;ASME SB161-2019 Seamless nickel pipe, suitable for foreign investment projects and export orders;ASME SB163-2019 seamless nickel pipe, for Ni201 material, for export high temperature service;EN 12451-2012 European Standard Nickel Copper Alloy Pipe for EU Export Projects;JIS H4551-2015 nickel pipe, suitable for Japanese and Southeast Asian projects.

IV. Project Application Reference Case

50% NaOH evaporation pipe in caustic soda plant is made of N4 material, Medium temperature 320℃, Specifications DN100, Wall thickness 3mm, Stable operation for 5 years without corrosion.Early project selection error, using N6 pipe collocationTitanium flangeAfter 3 months of service, stress corrosion cracking occurred in N6 pipe.After replacing all N4 matched nickel pipe fittings, the continuous operation condition is stable.Saturated sodium chloride pipeline of chlor-alkali plant, Medium 80℃, DN200 wall thickness 4mm N6 nickel tube, No pitting corrosion after 6 years operation, The pitting corrosion resistance of N6 is better than that of titanium under chloride ion condition, Economically good.Acetic acid condensation pipeline of chemical plant, Medium 200℃ acetic acid, DN80 wall thickness 2mm N4 nickel tube, Stable operation for 4 years without corrosionN6 pipe was selected in the early stage, graphitization embrittlement occurred in 2 years, and N4 was replaced to solve the failure problem.Pharmaceutical factory 10% dilute sulfuric acid pipeline, PTFE construction with N6 liner, Medium 60℃, DN50 wall thickness 1.5mm, Stable for 3 years, The lining scheme gives consideration to corrosion resistance and cost.High temperature organic solvent heat exchange tube, Material Ni201, Specifications DN25 Wall thickness 1.2mm, Implement ASME SB163-2019 standards, Export high temperature project priority to choose the brand and standard combination.

[Core Question 2] Why can't nickel tubes be matched?Titanium flangeUse? A: Nickel and titanium electrochemical properties are quite different, direct docking will produce galvanic corrosion.It is suggested that nickel pipe should be matched with nickel flange, or insulation gasket should be installed between flanges for isolation protection.

Five, five steps to avoid pit selection points

Pit avoidance 1: N6 shall be selected under high temperature and concentrated alkali conditions.Medium concentrated NaOH, temperature ≥300℃ choose N6, the material will graphitize embrittlement, 1-3 years cracking, temperature ≥300℃ concentrated alkali conditions, must choose N4. Pit avoidance 2: direct matching of nickel pipesTitanium flangeto the system.Galvanic corrosion formed by direct contact between nickel and titanium, The pipes will fail in half a year, Matching flange preferred nickel flange of the same material, Or add insulation spacer. Pit avoidance 3: nickel pipe is directly selected under hydrofluoric acid condition.Nickel has limited resistance to HF media, 1-2 Corrosion loss occurs every year, Hastelloy or monel is preferred for hydrofluoric acid service. Pit 4: The wall thickness of the pipe is not up to standard.Drawing requires wall thickness of 3mm, The actual supply is only 2mm, underpressure, 1-2 Annual pipeline failure, Ultrasonic thickness measurement after arrival, Weighing method verification. Pit avoidance 5: Perform standard mixing.Drawing Requirements ASME Standards, Supplier supplies according to GB/T, Deviation of pipe outer diameter exceeds standard, Unable to assemble on site, Verification MTC material certificate, The certificate shall be marked with standard number and specification information.

VI. Shaanxi Qianyi Tuoda Supporting Technical Services

Located in Baoji, China Titanium Valley, Shaanxi 100 billion Tuoda, Has many years of nickel non-standard products processing experience, Provide three supporting technical services.The first one-to-one type selection consultation, provide medium, temperature, concentration parameters, 10 minutes to issue a nickel tube brand selection scheme;The second spot resources, N4, N6 seamless nickel pipe DN15-DN300 specifications spot reserve sufficient;The third free MTC material review, submit material certificate, engineer 30 minutes to verify authenticity.Contact: 15909236031 / 0917-3557966, official website:http://www.sxqytd.com/

The core of nickel tube selection is not blindly selecting high-priced materials, but relying on the medium and temperature matching corresponding grades.Remember the three selection principles: concentrated alkali corrosion conditions priority nickel, titanium easy to occur alkali brittle;Temperature ≥300℃ Select N4;High temperature conditions for export projects adopt ASME SB163 standards. To learn more about nickel related technologies, please refer to the article in the station: 

"20 Questions about Common Marks of nickel plate"http://www.sxqytd.com/index.php/new/index/id/184.html 

Technical Guide for Nickel Flange Selectionhttp://www.sxqytd.com/index.php/new/index/id/187.html 

N6 nickel plate Selection Key Pointshttp://www.sxqytd.com/index.php/new/index/id/171.html

Technical reference standards in this paper: GB/T 2882-2013, ASME SB161-2019, ASME SB163-2019, EN 12451-2012, JIS H4551-2015.Updated: August 6, 2026. disclaimer, Nickel tube selection in this article, Media matching is for technical reference only, The actual service effect depends on the medium concentration, temperature, Field operation and maintenance factors, Formal project selection is subject to written technical confirmation by both parties.