Materials.Business Weekly ⚙️

February 16, 2021

Quote of the week: “I am a big fan of materials science.” — Elon Musk


From The Editor's Corner

STAINLESS STEEL; A FACT? - PART ll

A noble family

Let’s begin by recapping what we talked about in the last article. Steel was the material of the 19th Century, and stainless steel – SS - was the “noble,” or somewhat virtuous, the material of the 20th Century. Since its birth in the 1910s, it isn't easy to imagine a day going by without us using some form of SS. From as early as any of us can remember, SS has been in our kitchens and on our dining-tables, in hospitals, at the gym, as urban furniture, architecture, cars, and so on. SS is safe, hygienic (i.e., easy to wash and sterilize- a great trait nowadays!), toxin-free, durable, aesthetically appealing, and easy to maintain. SS is both corrosion resistant and also heat and fire-resistant and is referred to as a heat-resistant alloy. Besides its good mechanical properties, the reasons mentioned above explain its widespread use across major industries dealing with aqueous corrosion. Additionally, SS exhibits good behavior when high-temperature services are required (good oxidation resistance, creep, minor microstructure changes, and erosion-resistant), such as in the energy (nuclear, solar, coal, gas, etc.), chemical, and heavy industry.


An overview of the fundamentals of SS

SS is a group of steels that contain at least 10.5% Cr. This element can be quickly oxidized, creating a regenerative and passivating surface film of Cr2O3, highly adherent, transparent, and thin (2.0-5.0 nm). Usually, a good and protective film on the SS is formed if temperature and corrosive environment are moderated. Some other alloying elements, such as Ni, are often used. According to the percentage of alloying, microstructure and other factors consequently change, thus giving rise to the different properties of SS, categorized by families. The most common categories of SS, according to microstructure at room temperature, are as follows:

​- Austenitic: Contains at least 16% Cr and 6% Ni. The primary type is 304 or 18-8. Type 301 is also widely used.

- Ferritic: 10.5 to 18% Cr. Grades as 409 and 430 are some examples.

- Martensitic: Cr is the main alloying-element, but contains a lower percentage than ferritic and a higher C content. Some examples include grades 410, 416, 420, and 440.

- Duplex: A mixture of austenite and ferrite. Examples are types 2205 and 2304.

- Precipitation Hardening, PH: Cr-Ni steels can develop very high tensile strengths by the microstructural modification of their martensitic constituent. The typical example is type 630 or 17-4 PH, containing 15-17.5% Cr, 3-5% Ni, and 3-5% Cu.

​When talking about the alloying elements' primary role, we found that Cr forms the passivation film, retarding the inward diffusion of oxygen towards the steel substrate, thus obstructing any further attack. Meanwhile, Ni increases ductility, high-temperature strength, and resistance to Cr2O3 decomposition by carburization or nitridation. SS with Mo content lower than 3% increase creep strength. B also increases creep resistance. Small and controlled amounts of N and C enhance creep strength too. Ti and Nb promote the sigma-phase formation and increase strength in austenitic SS. Small earth metal additions such as cerium or lanthanum significantly improve film adherence, mainly under thermal cycling exposure.

SS is not stainless

Breaking the passive film

Bearing in mind the protection mechanism, SS has limitations when the passivation film either is not well-formed or fails for any reason, the SS then becomes corroded. Like other passivated metals, SS is also prone to corrosion by pitting. This situation frequently happens in conditions with chloride exposure because the small Cl- ion can penetrate the passivation film. The depolarization of a small area on the substrate occurs, and a dissolution process starts. It is a situation where the relationship between cathodic and anodic areas becomes very favorable for a quick penetration attack in a localized point. Then, the rest of the pitting mechanism happens. Such an attack can explain all cases of SS corrosion involving a very aggressive environment. Another problem that concerns the film’s breaking is related to erosive stresses that avoid the passivation, thus allowing the substrate’s exposure to a permanent attack by the corrosive environment. In the end, a simultaneous effect of corrosion and mechanical efforts results in a problem of corrosion/erosion.

Sensitizing

Another risk appears when some microstructure regions become depleted in Cr due to factors such as high-temperature diffusion and reactions with C or N that form carbides or nitrides. The affected region of the SS becomes “sensitized,” and corrosion subsequently happens. Such occurrences related to the SS behavior at high temperatures become common when SS is welded without following recommended practices and the neighbor region turns depleted on Cr. Therefore, SS welding has become a severe matter of concern and is a topic of intensive research. In most cases, there are solutions. For example, corrosion resistance at temperatures as high as 1000 °C can be achieved with Cr contents between 25 and 30%, while carburization can be limited using extra-low C contents (grades “L”) or higher Ni concentrations.

Stress Corrosion Cracking

Sometimes, SCC happens, where one of the inductors is the chloride ion, but the starting condition is related to local residual stresses into the SS. Here, duplex SS shows better behavior resisting corrosive attack and supporting SCC better due to its mixture of ferrite and austenite. This mixture allows the avoidance of the crack’s propagation after its initiation. Sometimes, heat treatment is a suitable solution, too.

Conditions like a crevice, other concentration cell possibilities, or galvanic couples are additional risks for SS corrosion. Taking additional anticorrosive measures is useful more of the time. The starting point usually is a proper design and selection of materials. Then, counter measurement technologies like cathodic protection, hardening, and special coatings, which have been developed in the last 3-4 decades, are then applied accordingly. And finally, to have a real stainless-steel means to have adequate training in executing the right project design, choosing the suitable material for the desired application, and how to use and care for the SS. All of these are crucial steps for “well-behaving” SS, particularly for critical conditions.

Occurring developments

Products

Looking for a ‘better behaving’ SS, researchers in companies and academics are hard at work in increasingly demanding service conditions. Regarding the market, we found new products like Sanicro® 35. According to the manufacturer, it is an alloy with a nominal composition of 35% Ni, 27% Cr, 6.5% Mo, 0.8% Mn, 0.3% N, 0.2% Cu, and ≤0.05% Si, ≤0.030% C, ≤0.030% P, ≤0.020% S. The resulting SS grade is characterized by its good behavior in conditions under risk of pitting and crevice corrosion, SCC, high acidic and caustic environments, erosion, and increased mechanical efforts. Products like the above come from past research, most of the time reported as patents or papers. The following point is just one example of the efforts that have been done over the last decades, confirming that although SS is ‘old’ material, it still has a bright future.


Inventions

A quick search in the US Patent Office database, USPTO, shows some impressive figures. Using the keywords such as “stainless” and “steel,” the total number of granted patents since the year 1790 (when the first USA Patent Act was established) is currently sitting at 1717. Between 1976 and now, 1597 patents have been awarded, with the latest one granted on February the 2nd, 2021. That means only 120 patents about SS were granted before 1976. Furthermore, when looking at these patents’ subjects, it is easy to identify that the inventions during the last decades are mainly related to new: alloys, products, processes, and applications in an exciting approach to the emerging technologies. To give an idea about the novelty of these patents, the following are the summaries of some of them (where some of the points of interest are in bold):

-Patent: “*Austenitic stainless-steel sheet for exhaust component having excellent heat resistance and workability, turbocharger component, and method for producing austenitic stainless-steel sheet for exhaust component*.”

- Patent:Ferritic stainless-steel foil.

- Patent:“Stainless steel substrate.

​Additionally, looking at the applications over the last 20 years shows a list of 1408 submitted patents, where the latest one was submitted on February 4th, 2021. Some of the latest applications include (where the points of interest are in bold):

- Application: “Ferritic stainless steel.”
- Application: “New duplex stainless steel.

- Application: “Stainless Steel Powder for Producing a Shaped Article.”
Behind the upcoming and future patents and products on the market, much more research is needed before. What are researching now and what issues must be investigated are themes of interest thinking about the future of SS. Right now is the perfect time to go more in-depth on this topic.

Remember: Protection of materials and equipment is a profitable business!

Prof. Carlos Arroyave, Ph.D. Editor.

www.arroyave.co


Materials Biz News

Trends on steelmaking

Stahl + Eisen has published the new 20th edition of the “Handbook of the European Iron and Steel Works.” This book is a source of current information about European steel corporations, including their profiles and recent developments on new technologies, materials, and products. Furthermore, statistics by country (production and trading) about raw materials and steel products are provided.

-Source-


Proper management of risk is a profitable business

ENGEN, a company member of the PETRONAS group, announced last December 4th a shutdown because a fire occurred at its refinery in Wentworth, Durban. It is the second-largest refinery in South Africa, with a capacity of 120.000 BPD. Last week, the National Parliament announced revoking the Engen operating permit until the refinery submits the investigation report and preventative measures to the authorities. According to the news, the cost of repairs is estimated at USD $55.000.000, and then the future of the refinery is not so clear.

-Read More-


Towards a better recognition of materials and asset management

Four Brazilian professional associations, including the Brazilian Association of Corrosion – ABRACO, the Brazilian Association of Non-Destructive Testing – ABENDI, the Brazilian Association of Maintenance and Asset Management - ABRAMAN, and the Brazilian Foundation of Welding Technology – FBTS, are joining efforts towards the awareness and recognition improvement of inspectors and their role. A call to join the initiative is open.

-Learn More-


Jobs

Taking care of pipeline corrosion problems for the energy industry Shorewood, USA.

Position: Corrosion Supervisor

Seeker: Kinder Morgan Inc.

Location: Shorewood, Illinois, USA

The basic profile of the candidate:

- Education: A technical degree in an electrical, electronic, or electro-mechanical program, and certification as NACE CP-2 or higher.

- Experience: Five or more years in pipeline corrosion control.

- Technical skills: Math skills to perform budget reconciliation and engineering calculations, adequate analytical and troubleshooting competencies, and strong computer skills.

- Physical requirements: Must be able to lift to 50 pounds, walk over uneven terrain, and withstand extreme weather conditions.

- Bonus: NACE CP-3 certification or higher.

Job description: Supervising all the issues concerning proper corrosion control facilities on high-pressure gas pipeline systems (design, installation, operation, and maintenance).


Caring the new materials and equipment Shangai, China

Position: Materials Test Engineer

Seeker: Tesla

Location: Shanghai, China

The basic profile of the candidate:

- Education: Advanced Degree in Metallurgy, Materials Engineering, or related field.

- Experience: Work with vendors and external test labs and work with hazardous materials.

- Technical skills: Must be able to effectively handle multiple priorities, organize workload, meet deadlines, and manage time independently.

- Bonus: Candidates with highly relevant work experience will also be considered.

Job description: The incumbent will be responsible for all materials and component-level testing, characterization, and failure analysis activities, both pre and post-fabrication, using various techniques, such as optical microscopy, SEM, EDS, PoDFA, OES, hardness, tensile, and bend testing.

Doing business for a more sustainable planet

UpLink is a global open digital platform fueled by the World Economic Forum and some other worldwide organizations. Its purpose is to put entrepreneurs and young innovators in front of the challenges concerning the Sustainable Development Goals – SDG – defined by the United Nations as the pathway for a better world for all in the coming decade. UpLink also contributes to joint forces between entrepreneurs and investors to accelerate solutions and deliver impact at scale. Following its actions, Uplink is currently asking for proposals about six subjects, most of them quickly related to solutions from corrosionists. The open call for proposals includes the following innovation areas:​

- Accelerating Clean Energy Transitions

- Clean Air for All

- Achieving Health Equity

- Mobilizing Action on Climate Change

- Climate Adaptation

- World's biggest Water Challenges


Networking & Knowledge Exchange

Talking about the near future of the O&G industry Virtual

Nowadays, it is easy to understand that the future of the sector is directly related to sustainability. This is why the Energy Institute is organizing the event entitled IP Week 2021: From Crisis to Low Carbon opportunity – A Decade of Delivery for the Oil and Gas Industry. The meeting will be held from February 23rd to 25th, 2021. The primary purpose of the plan is to look for urgent actions again the three current global challenges: “building a resilient recovery from the devastating COVID-19 pandemic; achieving the UN goal of universal access to energy for all populations; and charting an ambitious course - at COP26 and beyond - for tackling the threat we all face from the climate emergency.” Speakers are global leaders from the industry, academy, and government. According to the organizers, there are more than 1500 registered delegates and more than 200 companies coming from more than 50 countries.


New corrosion problems and solutions Virtual

The second monthly session of the CORROZOOM webinar series, organized by the Fontana Corrosion Center of the College of Engineering of the Ohio State University, Columbus, Ohio, USA, will be given by our colleague Nick Birbilis, from the Australian National University. The subject of the speech is “Corrosion of Additive Manufactured Materials.” Professor Birbilis is one of the more outstanding researchers on the corrosion mechanism of light and new alloys. His work includes several additive manufacturing technologies, exploration of new alloy compositions, microstructural studies, and corrosion assessment — issues to be considered in the scheduled seminar.

Date: Wednesday, February 24th, 2021.

Time: 8:00 - 9:00 EST (GMT – 5)

Pipelines integrity Virtual

Pipeline Pigging and Integrity Management - PPIM 2021, Conference and Exhibition. It is an event organized by Clarion Technical Conferences, supported by World Pipelines and North American Oil & Gas magazines, and sponsored by a group of companies related to the theme, to be held on February 24th and 25th of 2021. Some of the technical sessions included are risk assessment, engineering assessment, materials verification, cracks & seam welds, and education & competency assurance. PPIM 2021 also consists of a long list of exhibitors, providers of products and services, like Baker Hughes, DNV, Drinkwater Products, Linde Services, NDT Global, Olympus, ROSEN; T.D. Williamson, and Thermo Fisher Scientific.

Photo by Louis Hansel @shotsoflouis on Unsplash