Provided by Dr. Jim Hardy



When I started writing experimental techniques and lessons learned during the electrochemical operation of a high temperature autoclave, I first thought of the predecessors who were ahead of my adventure. This is just a partial list of individuals: they are researchers, equipment engineers, mentors and technicians working at Bettys and Knowles, who paved the way for me. Some of the names that come to my mind are Rick Garstka, Ted Druga, Bert Setterberg, Rudy Majcher, Jack Carr, Bob Rubino, Doug Thompson, Ken Granger, Rosemary Janik, Bill Archer, Garry Lynch, Irene Rosati, Mike Ochap, Dave Kedzierski, Keith Eklund, George Halbfinger, Mike Danielson, Yinfang Wang. The most important thing in the company that shared their story is Digby Macdonald, who laid the foundation for us and always wanted to share his experience with you.


The technical report will cover many topics where only hot water is the same. In order to adapt to the space constraints of technical reports, this article will be a collection of lessons. For their part, none of them is purely my own experience. The text will tell a series of enlightenments or memories, none of which is comprehensive. There may be detailed technical reports in the future to cover specific situations, but they have to wait for answers to some questions, and we hope that this technical report can help.



Safety is of the utmost importance when using high temperature autoclaves. Because energy is stored in water at high pressures and temperatures, the consequences of any accident can be very serious. Many people working in this field have encountered steam jets, or metal objects have fallen from the top of a bay that is more than thirty feet above. Some encountered a two-pound high-temperature autoclave that fell a quarter of a mile from the factory. This list of security measures is intended to stimulate further research and development. A study on the safety of high temperature autoclaves in a library or online will generate a number of documents to guide the development of the document. It is important that the documentation is completed under the guidance of all experts involved in the affected equipment, procedures and personnel. In addition, you need to consult an outside expert to ensure that no important things have been overlooked, and review and update the work requirements every year or any serious accident. All staff involved in work or around pressure equipment should be required to be trained, and the factory should post notices to inform the visitor of the hazard and provide protection.

Management and insurance requirements

In addition to the general guidelines and any localization requirements mentioned above, there are regulatory requirements and requirements imposed by insurance companies. This has led many large companies to establish internal committees to develop and implement these rules. It is a good method to inform the legal person and insurance company of the company that plans to operate the high temperature autoclave in advance. In addition to job requirements, some companies and insurance companies have appointed inspectors and industrial security departments to help departments and customers. Any jurisdiction from local to national jurisdictions may establish regulations, procedures for reviewing or operating high temperature autoclaves, and equipment operators should determine the relevant jurisdictions and regulations.

Good practice

Even when the request is not executed, there are some things you can do below. The order of the list is arbitrary, and the contents of the list are not comprehensive.

  1. Use a minimum pressure vessel that meets the requirements of the experiment.

  2. Temperature and pressure are continuously monitored to prevent accidents and reduce their severity.

  3. Install over temperature alarm and safety switch.

  4. The heater temperature is detected and limited to protect the container material.

  5. Install the pressure relief device and vent it safely.

  6. Use a suitable tether to prevent component spray. Thermocouples and electrodes are the best examples.

  7. Ensure that any sampling ports are properly protected and that wastewater is safely disposed of. This is especially important for toxic or corrosive materials. Any material that requires special handling in the laboratory is more dangerous in high temperature autoclaves.

  8. Usually glass components should be avoided as much as possible. Sudden power can break the glass, and many solutions will erode the glass at high temperatures. If a special component requires a glass or diamond window or manifold, a shielding device should be arranged.

High temperature autoclave and structural materials

高温高压釜有很多尺寸和形状,直径从1 毫英寸到1 米,高有几米。他们可以在高于环境压力几个kPa到数十MPa下操作。本身设计和选择材料由专家正确执行。同样地,建议任何想要建造或使用高温高压釜的人员去查阅ASME锅炉和压力容器的编码或者去获得任意压力容器用来建造和保持符合编码和本地要求的证书。Autoclave Engineers和Parr Engineering是两个设计和建造标准高温高压釜包和为他人提供设计和证书服务定制高温高压釜的两个公司。其他高温高压釜和腐蚀测试服务的供应者也可以制造高温高压釜和测试系统。在说明,购买和操作高温高压釜方面投资前,先咨询在你想做的测试方面富有经验的工作人员是明智的。





目前,在可靠制造商提供的水溶液体系中没有其他材料可以接近PTFE的性能。一些应用中更喜欢全氟烃基(PFA)PTFE ,因为它拥有更高的软化温度,所以它保持着某个结构强度直到280 ºC。不过,它在高于有效范围时软化得更加突然,很多偶然的温度变化导致了PFA绝缘材料的彻底坍塌。聚酰亚胺和环氧材料比 PTFE 有更高的熔点。不过,他们在低至150 ºC的温度水解,导致了绝缘材料的分解和测试溶液的污染。


很多关于塑料的考虑在使用其他材料做高温高压釜电化学的绝缘材料时也会有。大多数在室温和空气中我们认为理所当然的玻璃和陶瓷在高温和甚至适度提高pH时会被水侵蚀。玻璃腐蚀形成硅酸盐,氧化铝腐蚀形成了铝酸盐。蓝宝石和氧化铝用于一些应用,但是很多研究人员对一批次品陶瓷或者把实验推向更高的pH或温度而失望。氧化钇完全稳定的氧化锆(YSZ)是唯一广泛应用的陶瓷,它能够耐受150ºC以上水的侵蚀和大于1M NaOH溶液的侵蚀。对于其他材料,制造商必须仔细挑选。部分稳定的氧化锆因为更高的强度和韧性被广泛用于机械应用,但是他们容易被热水侵蚀。有时候出自同一制造商的许多材料在热水中更容易软化。YSZ有半导体性质,这在高温电化学中很有用,并且很多变化。



在一个密封高温高压釜内,氧气量几乎常常不是我们预想的。如果有人在准备一个无氧测试,空气将被困在裂缝中,即使在容器被抽真空并用惰性气体洗净后。在加热时,吸附气体和腐蚀膜可以分解释放氧气。如果有人计划了一个定量的氧气,未知量的氧化物在暴露金属表面形成。使用除氧剂有时足以从系统将它消除,提供不会影响测试的除气产物。在容器顶部的蒸汽空间保持一个固定的气体成分可以通过亨利定律(Henry’s law)来控制溶液的成分,但是只有当系统充分地混合而且氧气在容器中腐蚀的消耗速率没有超过质量传输速率时才可以。这整个图景被空气可以通过裂缝扩散进来从而建立稳定低含量氧的事实进一步复杂化了。


可以通过采样或连续分析可以对压力容器进行氧分析。采样是最经济的方法,Chemets®,自填充安瓶和色度分析试剂被广泛地用于这个目的(1)。采样最大的缺点是缺乏一致性:一个经验丰富的操作者可以连续地测量氧含量直到20ppb或更少,但是很多有经验的操作者不能测量少于100ppb。一旦在流动系统中正确地建立和校准,固定的氧分析器可以测量测量值的1%直到低于1ppb。极谱分析传感器仅可在300kPa内使用,所以他们常用在流向排水或流向用泵补给的系统的管道上。对于压力高达30 MPa时,Orbisphere用更高的价格制造了高精准和高敏感的分析器。基于荧光猝灭的氧气分析器接近测量几个ppb氧气所需的敏感度。任何有这个需求的人们应该咨询InSitu Instruments,Orbisphere和Ocean Optics来确定他们的目前的能力,并且询问作者关于最新的测试结果。(i),(ii),(iii



看过几页机械问题之后,我们可以开始电化学应用了。如在高温高压釜中所见遍及电化学讨论的一个概念是高温时在水中的腐蚀与室温时大有不同。举个例子,H2O-H2/O2的交换速率是快得多。他们接近氧化还原平衡,可以控制很多电化学测量。高温也能导致腐蚀产生的氢气,这会影响腐蚀反应的速率。有时候在密闭容器中的腐蚀速率可以与排除H2和O2 的循环容器中测得的非常得不同。这个讨论将仅限于一些最广泛使用的技术。几乎所有已知的电化学技术可以被应用于高温高压釜,虽然一些从机理角度是禁止的。一些技术已经特别发展以利用高温高压釜可得的温度和压力的优势。













有经验的电化学家早已改装传统参比电极用于高温高压釜,不过像氯化银这样的沉淀溶解的增加和高温扩散率的增加使他们很难用而且不精确。当Digby Macdonald推出了压力平衡参比电极(PBRE, iv)时,这个现象改观了。取代固定容器,PBRE包含了一个灵活的盐桥的组件,不可渗透的膜,通常是PTFE。结果,会从参比电解池压出控制溶液或者引入污染物以影响电势的压力的变化会被参比电解池中的等效压力平衡掉。参比电解池的成分保持了,参比电势可以像现有热动力学数据那样精确地计算了。



当有人会从上述PBRE讨论中推导出,理想的参比电极会有一个不能渗透的连接去测试溶液。典型的玻璃pH电极有这个,而且如果测试溶液的pH是已知的且为常数或者被连续测得的话将制得一个优秀的第二参比。不幸的是,玻璃pH电极中的玻璃像任何其他的玻璃一样会被热水侵蚀。它也非常薄且脆,是压力条件下的一个不好的选择。不过,与一些应用中充当结构和绝缘材料陶瓷相同的YSZ陶瓷也有半导体性质,能在高温传导氧离子。和一个内部参比电解池像Hg/HgCl or Fe/Fe2O3一起,封闭式YSZ管可以通过如下反应充当一个pH电极:

OH- + OH- ↔ H2O + O-2


H+ + OH- ↔ H2O

具有Fe/Fe2O3 或者 Cu/Cu2O内部参比连接的传感器被广泛地用于高温高压釜在溶液中的测试,溶液的pH是已知的且为常数。(vi, vii)通过选择需要的性质,YSZ pH传感器已经被用到低至90ºC。(viii




Stress corrosion cracking is a very important issue and often requires a high temperature autoclave to produce some of the conditions in which it appears and is studied. Similarly, it has a large amount of relevant literature, and this technical report will not explore this topic. Some high temperature autoclave tests have proven unique considerations as follows:

A. Load/displacement control can be affected by changes in temperature, and sample fatigue increases at an alarming rate.

B. Crack monitoring techniques can produce unintended electrochemical results, as can be inferred from the EPD paragraph. Displacement measurements, although in principle non-destructive testing, also require sensitive equipment to detect the effects of corrosion and electrochemistry.

chapter summary

Electrochemistry is fun and exciting. This is especially true in high temperature autoclaves. Be careful when planning your experiment. Consult with experienced companies and individuals about the specific technology you want to apply. Therefore, the work costs a lot of money to implement properly. Remember that safety is the most important thing.

References and additional reading

Readers are referred to the publications in the references. These publications will lead to other readings that will reveal the work of a large number of Digby Macdonald and other pioneers in this field. ( ix ) Contact the author to make additional recommendations on specific topics.

About the author

 James Hardy is the head of ChemCorr LLC, a consulting firm dealing with chemical, corrosion, electrochemical and chemical kinetics. He worked in the Betis Atomic Energy Laboratory from 1987 to 2009 on high temperature and high pressure water chemistry, chemical instrumentation and corrosion modelling and control. He is employed by Exxon Research to control the development of difficult resources such as coal and oil shale. He received his Ph.D. in physical chemistry from the University of Texas (1976). James is a member of NACE, ASTM and the International Combustion Society. You can contact him via am.

Chemets: Self-filling ampoules for water analysis; browse  http://www.chemetrics.com/Oxygen+%28dissolved%29 ; The ASTM Reference: ASTM 11.01, ASTM D 5543-94 (2005), Standard Low Level Water Soluble Oxygen Test method

i. http://www.in-situ.com/, In-Situ, Inc.

ii. http://oceanoptics.com/, Ocean Optics, Inc.

iii. http://www.hach.com, Hach Ultra Instruments, makers of Orbisphere electrochemical and fluorescent analyzers.

iv. D. D. Macdonald, "Reference Electrodes for High Temperature Aqueous Systems-A Review and Assessment," Corrosion, 34, (76-84), 1978.

v. M.J. Danielson, Corrosion, 35, (1979) p. 200; and Corrosion, 39, (1983) p. 202.

vi. Digby D. MacDonald; Ting Zhu; Xueyong Guan, “Current state-of-the-art in reference electrode technology for use in high subcritical and supercritical aqueous systems” European Federation of Corrosion Publications (2007), 49(Electrochemistry in Light Water Reactors), 3-42. Publisher: Woodhead Publishing Ltd., CODEN: EFCPE4 ISSN: 1354-5116. Journal.

vii. Although the calomel electrode (Hg/HgCl) is a better reference than Cu/CuO or Fe/FeO because its potential is well defined, it is excluded from most applications by the use of mercury. Besides its toxicity, mercury can cause liquid metal embrittlement, which can destroy autoclaves. Good operating practices exclude all mercury from any autoclave facility.

viii. Private communications from Lietai Yang and Corr Instruments, http://www.corrinstruments.com/.

ix. Techniques for Corrosion Monitoring, (L. Yang, ed., Woodhead Publishing, Success, UK 2008).