Materials.Business Weekly ⚙️
December 15, 2020
Quote of the week: “Creativity is contagious. Pass it on.” — Albert Einstein.
From The Editor's Corner
CLEANING IS HEALTHY!
Good and bad coatings
Some of the lessons learned from the current situation of the pandemic concern the relevance of cleanliness. History talks about the black plague’s lower infection within the Jewish community, due to their practice of washing their hands frequently. More recently, mirroring the 1300s, yet another discovery about the importance of hand-washing was made, however this time it included midwives and doctors washing their hands during birth and post-natal care of babies. Just only a few examples showing that cleaning is healthy for people. Likewise, it is healthy for materials, too! Many times cleaning surfaces is also essential so that there is no risk of spreading viruses and bacteria. Just as cleaning is good for living beings, it is also important for materials. Although there are a lot of protective coatings (paints, passivation films, protective rusts, and so on), many other “coatings” or rather layers of surface pollutants, accumulate on the material surface and promote chemical or electrochemical reactions, causing unexpected corrosion cells most of the time.
Wash your materials and equipment
We are talking about deposits of the crust of sooting formed after centuries, spoiling old buildings, sculptures, and other urban structures. Usually, we are very worried about dust collecting on our car because everyone knows the negative effect of not washing it regularly. Simple but salient corrosion engineering practice is to wash structures and equipment exposed to marine atmospheres, in an attempt to avoid pitting and other corrosion problems. In particular, passivated surfaces of stainless steel and aluminum alloys that are susceptible to pitting attack must be protected against the effect of dirt deposits. Sometimes, pollutants are reactive and can react on the surface of interest, attacking and dissolving the substrate. This is the case with salts and ionic species prompting electrolyte formation, or increasing its conductivity. Inert pollutants can contribute to the establishment of aeration cells, cathodic points against the substrate, and so on. Of course, multiple, and simultaneous deleterious effects are also possible. Most of the time, surface contamination is visible, however, sometimes it is not.
Prepare the surface before coating it
Usually, when talking about corrosion and anticorrosion, we are referring to surface science and engineering because most of the time corrosion happens on the surface. For example, let’s talk about painting. It is a physicochemical interaction, and the efficiency of the protection depends on variables like adhesion to the surface. Consequently, surface preparation before the painting process is essential, and the characteristics of the interface substrate/coating becomes central. Empirical evidence shows the need for a good cleaning before painting as confirmed by scientific studies, such as the results of the research done by J.E. O. Mayne in 1959 in his paper called “the problem of painting rusty steel”. One of Mayne’s findings was concerned with seasonal degradation effects. He demonstrated that this effect was due to the presence of FeSO4 in the rust. During the winter months (at which time the atmosphere reached its highest levels of SO2) the FeSO4 content in the rust was higher). Similar issues can happen with mill scale or calamine, residues of old paints, and other visible deposits on the surface to be painted. Since decades ago, cleaning of the surface is mandatory and several international standards regulate the degree of preparation according to each situation. Preparation can be either chemical or mechanical, but most of the time the latter is preferred, which includes hand and electrical tools, abrasive blast cleaning, using both solid particles(sand or other ceramics, metallic, slag, and others), and high-pressure fluids (water usually). In my personal experience, there was once a group of steel coupons, prepared by the same people and protected with the same coating system, were exposed to the Caribbean seashore. A subgroup of these steel coupons demonstrated some kind of corrosion attack after 2 years, and the rest only after five. The sole difference was the preparation place (a lab in Cartagena de Indias for the first subgroup and a lab in Medellin for the others). In other words, we are talking about invisible pollutants, or soluble salts that also have a great impact on the painting behavior and, consequently, have to also be removed, as a guarantee of anticorrosive protection by paints and coatings.
A heuristic approach
In the 1970s some organizations began to demand preparation-work for painting including acceptable maximum levels of species like chlorides. Some years later, researchers started to study the problem. A team from the National Center for Metallurgical Research, in Madrid, led by Prof. Manuel Morcillo began a systematic approach towards the subject. After almost 30 years of their best efforts, including several international projects, various doctoral theses, and numerous papers, there is now a good amount of knowledge of the incidence of soluble salts in the behavior of anticorrosive paints. Additionally, international standardization organizations started to drive concerns and procedures to be considered in each scenario of painting surfaces. Companies started to market products and services related to the issue. Some of the research questions explored included what chemical substances or combinations thereof are capable of interacting with the underlying metal and producing premature deterioration of the paint coating? What role is played by the environment when the coating applied to a contaminated surface is exposed? How do different paint systems behave in these situations? What is the role of the paint system’s thickness or the presence of corrosion-inhibiting pigments? Does the phenomenon take place only on steel substrates or is it independent of the metallic substrate?
Some of the answers
Some of the main reasons for surface contamination by soluble and invisible salts include the exposure of the material to polluted atmospheres, chlorides from de-icing salts, cleaning waters used for the surface treatment processes, polluted abrasives used for sandblasting (chlorides, sulfates, fluorides, etc.), old paint residues, wrong handling of materials (sweat, footsteps, fingerprints grease, wetting, and so on), construction materials (gypsum, anhydrite, etc.), and degradation of some kinds of binders (chlorinated rubber, polyvinyl or other chlorine-containing polymers).
Nowadays, we know that the main degradation mechanisms are because of soluble salts remaining in the interface between substrate and paint, which are osmotic blistering and underfilm corrosion. Osmotic blistering happens when the semipermeable layer of paint is crossed by water from the outside, forced by the osmotic pressure established by the gradient of concentration promoted by species in the interface like Cl- and SO42- who are eager to react with water. In the end, conditions under the film of paint are ideal for corrosion development. Aggressive ions in a water-electrolyte wet the substrate directly. Metals dissolution, rust formation, loss of adherence, improved conditions for the corrosion process, and a cyclic deterioration process take place. The limiting reagent in the corrosion reaction is oxygen diffusing through the paint. The kinetics of the deterioration process is then governed by the osmotic pressure, the ionic conductivity, the oxygen solubility of the aqueous electrolyte solution, and the water solubility of the corrosion products. When the substrate is rusty, the cathodic reaction governing under film corrosion occurs on the rust, and oxygen diffusion becomes a secondary factor. Once the corrosion attack is activated, the level of pollutants is heterogeneously distributed and placed mainly inside pits and intricate cavities, and it seems to become a secondary variable. The found detrimental effect goes from highest to lowest, as follows Cl- > NO3- > SO42- > NH4+ > Ca2+ > Na+. Sometimes, synergetic or additive effect by two or more pollutants may be observed.
Behavior according to the paint system
A relevant variable is a system applied as an anticorrosive coating, whereby the behavior depends on the nature of the paint and the mechanism of protection. The degree of osmotic blistering is directly associated with the permeability of the coating, and the underfilm corrosion rate will depend on the electrochemical influence of the coating. “Each case is a case”, and there are no general rules about the expected behavior. Depending on nature (types of binders, fillers, pigments, and other additives included in its formulation) and thickness in some systems, deterioration appears very quickly than that in others, but in general, the coating failure happens in a shorter time than expected. However, in the case of zinc-rich primers blistering did not usually happen and their behavior is good. In some cases, a pigment in the paint can cause inert pollutants as it happened with Pb-rich paints used earlier, or the rust converters (v.gr. phosphates) transforming them into insoluble compounds.
Measurement, critical levels, and removal
In addition to laboratory procedure for the extraction and measurement of the concentration of soluble salts, some automated or manual methods are useful in the field, some of which are available in retail. Swabbing, the Bresle patch, and the sleeve test are such examples. Their performance is sufficient not on rusty surfaces because, with the presence of rust, removal of contaminants decreases due to the entrapment of contaminants inside and below the corrosion products. Usual levels of extraction are lower than 100% (according to a lab method). Another limitation is related to the lack of reliable data about contaminant concentrations in practical situations. By practical considerations, some intentions of asking for zero pollutants have been disregarded. But universal critical upper limits are not so clearly established and there is no consensus yet, and current guidelines are highly controversial. Nevertheless, in the case of steel, there are some recommended upper limits according to the exposure conditions. For instance, 3 µg/cm2 for immersion service, 5 µg/cm2 for alternated immersion, and 10 µg/cm2 for atmospheric service exposure. In the same way, complete elimination of the surface pollutants is difficult to achieve. High-pressure water blasting, followed by dry blasting seems to be one of the more appropriate methods.
In summary, contamination of a surface by soluble salts is a matter of fact regarding the behavior of any anti-corrosive protective coating. The cleanest possible surface must have a purpose in any case. There are still major limitations on how to ensure safe these procedures are, but understanding how the phenomena can happen helps prevent premature failures from occurring. Considering the substrate, the environment, and how they interact will help a lot in the details to take care of when preparing the surface and selecting the painting system. It is a cost that should not be avoided. As always, proper anticorrosive protection pays. Remember: Protection of materials and equipment is good business!
Prof. Carlos Arroyave, Ph.D. Editor.
Materials Biz News
ASM International, The Materials Information Society, in partnership with some other associations and editorial companies, publishes a group of renowned journals concerning materials science and engineering. Currently, ASM is promoting higher access to the valuable papers published in such journals, highlighting a journal per month. Consequently, a group of selected papers is open for free access. The selected journal this December has been the Journal of Failure Analysis and Prevention (JFAP), and the Editor-in-Chief Michel E. Stevenson has chosen the following five interesting papers now available, free of charge:
- Preload from Tightening and Removal Torque
- Root Cause Analysis of an Oil-Burning Tabletop Torch Explosion
- Failure Analysis of Additively Manufactured Polyester Test Specimens Exposed to Various Liquid Media
- Investigation and Recommendations on Bottom-Dented Petroleum Pipelines
- Analyzing the Failure of Welded Steel Components in Construction Systems
Iron oxides for good
In agreement with environmental concerns (an option to the hot urban spots ) and aesthetic trends, black dyes are becoming more demanded in the construction industry. As an answer, Lanxess AG has expanded its capacity for black synthetic iron-oxide pigments at its Krefeld-Uerdingen (Rhine basin, Germany) site by more than 5.000 tons per year. The pigment is produced following the Laux process, which is protected by the USPTO US7425234B2 patent, Lanxess property, and expiring in 2024.
Tips about how to plan an (energy) construction project
Following, there is a list of ten useful recommendations to take into account in front of engineering duties as the above-mentioned and related ones. According to the authors, Jacqueline Greenberg Vogt and Robert C. Epstein from the attorney company Greenberg Traurig LLP, the purpose of the advice is to avoid headaches concerning defects in design or construction, completions after scheduled, overruns, and conflicts among the parties when companies are facing such kind of challenges. Suggestions are:
- Careful contracting
- Independent cost estimates
- Establish a firm budget
- Use “add and delete” alternatives
- Peer review the design
- Review the plans for constructability
- Set a reasonable schedule for construction
- Submittals as communication between contractor, designer, and owner
- Review of construction activities
- Periodic audits of contractor billing
Additive manufacturing maturing
In the frame of the “Additive Technologies, Expanding Horizons Leader Forum, the last 3rd of December was signed a memorandum for the creation of a Russian association for the development of additive technologies. The main purpose of the Association is to transform Russia into an additive manufacturing leader. According to the plans, the Country will have 180 centers by 2030 and a market of $2.400 million US dollars. Products for the nuclear and maritime industries are some of the current goals.
Competitive position in China Jiangbei, China.
The College of Chemical Engineering of the Nanjing Technical University (Jiangbei New District, Nanjing City, Jiangsu Province), a comprehensive institution focused on engineering, is offering a vacancy for a full professor. Right now, The Chemical Engineering program at NJtech is ranked as a First Level National Key program. The position is open for candidates with a Ph.D. degree in Chemical Engineering or related disciplines, and specialization in subjects such as energy, engineering, environmental, green chemistry, materials, or polymers. A minimum of three years of overseas working experience is another requirement. Duties will be related to teaching at the graduate level and direction and promotion of the program to top-tier international level.
Interested people, please send your CV to Ms. Meigui Xu. Email: [email protected]
A metallurgist for the energy transition Brande, Denmark.
Siemens Gamesa Renewable Energy, Brande – Denmark, is looking for a person with an M.Sc. degree in Materials Science, Chemical or Mechanical Engineering, or similar - possibly combined with a relevant Ph.D. degree, and specialized within the area metallurgy. Experience working as a metallurgist is a bonus, and experience working with characterization techniques such as light optical microscopy, scanning electron microscopy, X-Ray diffractometry, glow-discharge emission spectroscopy, and hardness measurements, as well. The responsibilities to be assumed will be related to R&D projects and non-destructive testing and characterization of ferrous alloys for wind turbine technologies and green energies in general.
Temporary, full-time position as Crystallographer & Course Instructor Guelph, Canada.
The Department of Chemistry, a central academic unit within the University of Guelph’s College of Engineering and Physical Sciences, Guelph, Ontario, one of Canada’s Top 50 Research Universities, is seeking a course instructor in crystallography for a temporary position from May 3rd 2021 to April 28th 2023. Some of the requirements are a Ph.D. degree in Chemistry plus 1 year of related experience or an equivalent combination of education and experience dealing with a small-molecule crystallographer for single crystal (SCXRD) and powder X-ray diffraction (PXRD) experiments. The successful candidate will: encourage and support widespread usage of the "X-lab" infrastructure beyond the Department of Chemistry; provide expertise and writing skills to support grant applications for future replacement of "X-lab" infrastructure as needed; teach and develop existing and new undergraduate and graduate courses within the Department of Chemistry.
Researching materials protection at the Red Sea Red Sea, Saudi Arabia.
KAUST, the King Abdullah University of Science and Technology, is an international private graduate-level science and technology research university located in Thuwal, on the shores of the Red Sea in Saudi Arabia. Currently, KAUST is offering fully funded scholarships to develop any of its graduate programs, including studies in several topics as corrosion and anticorrosion.
Networking & Knowledge Exchange
Expanded attendance opportunity Virtual
The European branch of NACE International recently organized a virtual meeting on “European Corrosion Management”. Currently, they are offering the option of post/event registration. According to the announcement by the organizers, post/registered people will have the opportunity to access on-demand and learn at your convenience from more than 40 presentations that cover topics from corrosion management best practices across multiple industries, to some of the hottest corrosion-related topics, including leveraging nonmetallic materials to help reduce corrosion failures and costs.
Learning for the New Normal Virtual
The Australasian Corrosion Association is announcing some of the coming technical training courses for the coming year. Subjects and data include:
- SSPC Concrete Coating Inspector, Feb 8-12
- NACE Coating Inspector Program Level 1, Feb 15-19
- NACE Coating Inspector Program Level 2, Feb 22-26
Strategic asset integrity management Virtual
Once again, NACE offers the opportunity of learning and training on how to handle corrosion and anticorrosive issues at the highest level of the company, and as part of the corporate strategy to improve both societal, environmental, and budgetary commitments. In principle, the program is designed for attendants with a bachelor’s degree in engineering plus 3+ work experience, and/or post-graduate degrees, asset owners, C-suite executives, senior-level managers, corrosion management consultants, asset management strategists, and IMPACT Plus licensees. The next class will be held on January 6th 2021, from 8:00 to 10:00 CT (USA)
The packaging is a matter of concern for corrosionists, too Podcast
A new episode of the European Patent Office podcast “Talk Innovation” has been broadcasted, entitled “Patents in progress - Thinking outside the box: Packaging technologies''. It is dealing with packaging technologies and patents about that. Concerns about environmental and other issues are discussed. Most of them related to materials protection in the age of the Circular Economy. Certainly, challenges for corrosionists are increasing!