Corrosion resistance of Nickel alloys in dilute and anhydrous hydrofluoric acid

Anhydrous hydrogen fluoride and hydrofluoric acid are major industrial process materials. Hydrofluoric acid is highly corrosive and extremely reactive, it is used in large magnitudes for pickling of stainless steels as well as other metals. Additionally, it is used in acid treatment of wells and glass etching. Other applications of hydrofluoric acid include production of aluminium fluoride and synthetic cryolite, fluorinated organics like aerosol propellants and plastics.

Anhydrous hydrogen fluoride is the basis of fluorocarbon industry that mainly includes coolants, fire extinguishing elements, ultrasonic cleaning fluids and fluorocarbon plastics.

Hydrofluoric acid in aqueous and anhydrous form is extremely hazardous that it severely affects eyes, lungs and mucous membranes.

Anhydrous hydrogen fluoride is made by the reaction of sulfuric acid and calcium fluoride. Commonly used materials for hydrofluoric acid service are carbon and alloy steels, stainless steels, aluminium, copper and nickel and nickel alloys.

Nickel and its alloys

Nickel 200 is less resistant than Monel 400 to aqueous  hydrofluoric acid. Oxygen has higher accelerating effect on corrosion of Nickel 200. In aqueous hydrofluoric acid, use of Nickel 200 is limited to air-free systems below 80oC. However there are cases of stress corrosion cracking of Nickel 200 in aqueous hydrofluoric acid, they seem to be associated to contaminants like cupric fluoride. Nickel 200 is highly resistant to hot anhydrous fluoride however it may be embrittled by sulfur compound contaminants.

Monel 400: Alloy 400 is widely used in hydrofluoric acid alkylation units and in the production of hydrofluoric acid. It has supreme resistance to liquid hydrofluoric acid over the whole concentration range in the absence of oxygen to minimum 150oC.

Monel 400 resists stress corrosion cracking when subjected to wet vapors of hydrofluoric acid in the presence of oxygen. Intergranular cracking occurs. In one test, alloy 400 received transgranular stress corrosion cracking in the vapour phase of dilute hydrofluoric acid solutions at temperatures up to 95oC. The cracking sensitivity was not based on the presence of oxygen and no cracking was noticed in the liquid phase.

The cracking mechanism was unknown until it was noticed that aqueous hydrofluoric acid solutions comprising significant concentrations of cupric chloride would result in fast cracking of stressed Monel 400. Nominally resistant nickel-copper composition corresponds to that Monel 400.

Stress corrosion cracking is often limited to the vapour phase rather than liquid is enrichment of a thin layer of aqueous hydrofluoric acid in the vapour with copper fluoride corrosion products. The availability of oxygen speeds up corrosion and develops CuF2 from CuF. The much greater dilution of corrosion products prevents reaching a critical concentration of CuF2 in the liquid phase.

Inconel 600: Alloy 600 resists corrosion in dilute aqueous hydrofluoric acid at ambient temperatures and anhydrous hydrogen fluoride. It is used in valves and other systems replacing alloy 400 to prevent the feasible stress corrosion cracking. It is commonly used for hot hydrofluoric acid vapors, preventing chemical resistance and providing good metallurgical stability.

High performance Nickel alloys: Hastelloy alloys like grade C276, B2 and G grades as well as Inconel 625 offer supreme resistance to aqueous and anhydrous hydrofluoric acid and to high temperature hydrofluoric acid vapors.  

Behavioural approaches of Nickel alloys to NaOH solutions

Corrosion resistance of pure nickel-chromium alloys is determined to find their usefulness in the different temperature-concentration ranges with respect to general corrosion rate and stress corrosion cracking susceptibility.

In boiling 10% NaoH at 103oC, different alloys such as Monel 400, Inconel 600, Inconel 625, Hastelloy C276, Hastelloy C4, C22 and C2000 are tested to determine their low corrosion rates irrespective of nickel concentration. In a solution of boiling 50% NaOH at 14oC and 70% NaoH boiling at temperature of 182oC, the tested alloys show nominal corrosion rates. Inconel 600 and Monel 400 are the commonly used materials to handle hot concentrated caustic. They also offer supreme corrosion resistance at all concentration as anticipated.

In boiling 50% NaOH an anticipated advantageous effect of increasing nickel concentration is observed. It is found that critical nickel concentration for corrosion resistance in this solution is almost half. Although 20 to 30% nickel concentrations also offer a wide enhancement as compare to stainless steel 304.

Nickel alloys containing iron and chromium such Inconel 600 is distinguished by its excellent resistance to uniform surface corrosion and to stress corrosion cracking in NaOH solutions. During testing Inconel 600 in 10% NaOH solutions at temperature of 325oC and pressure of 275 MPa, where there is no sign of cracking after 100 hours.

With the systematic evaluation of the damage to components made from Nickel and Inconel 600, the sensitivity to stress corrosion cracking of the both alloys is observed for the given temperature and concentration limit. Application of nickel is larger than Inconel 600.

Carbon concentration and heat processing have a remarkable effect on the stress corrosion cracking behaviour of Inconel 600. Outcomes of stress corrosion cracking tests following the slow strain rates in 10% NaOH solutions at 288oC are observed. Alloy 600 pipes containing carbon are tested.

The percent part of intergranular fracture on the fracture surface of the failed samples was accounted as a measure of the sensitivity to stress corrosion cracking . For the samples in the as-delivered state, the intergranular fracture part that is the sensitivity to stress corrosion cracking, reduced with increase in carbon concentration to reach a minimum 0.05%C. Resistance to stress corrosion cracking significantly increased by after heat processing and carbon concentration had eventually no influence.

Inconel 600 with modified carbon concentration and heat processing and test temperature did not have a considerable effect on the stress corrosion cracking behaviour.

For most of the tested alloys, the U bend samples are the more critical test condition as compared to the C ring samples. The ferritic and martenisitic stainless steels showed significant resistance to stress corrosion cracking, although the excellent general corrosion and the risk to embrittlement restricts their user under specific conditions. For the austenitic alloys, more highly stressed U bend samples showed that the resistance to stress corrosion cracking increased with increase in nickel concentration. The alloys with low nickel concentrations could not perform in the concentrated NaOH solutions.

Applications of advanced woven mesh screens

Heanjia is a worldwide leader in the applications of its two core competences, advanced metal transformation and materials and coatings. Heanjia offers solutions for the challenging filtration applications. We are your specialized partner in the design and production of filter elements and filtration systems. Our skills and experience in all aspects of filtration technology guarantee the product efficiency.

We can react to any situation and find solution to specific applications. For standard or tailored solutions, we offer you the screens to perfectly match your quality, productivity, handling and maintenance needs.

Aimed to become your specialized partner, we strive to provide products and solutions that meet your needs efficiently.

Wire mesh filter screens have common applications in:

Film, Synthetic fibers, PET bottle, Extrusion, Polycarbonate, Rubbers and silicones, Resins and paints and Hot melts.

We offer standard or custom made filter screens to immaculately match your quality. The best filter screens and the suitable elements are used in monomer, pre-polymer and polymer filter screens. Defy us and we will find the special solutions for your specific applications.

We can provide you with the complete set of elements such as sintered mesh for spinpack filtration. It is critical for the production of synthetic fiber, and we can exactly improve and enhance your conventional filtration process.

You can benefit with our metal to metal screens that are used in the polymer industry. Alloys used to produce these screens are: aluminium, copper, stainless steel, Inconel and others. The screens are made in any shape or dimensions.

Use of high quality screens allows significant reduction in the consumption of filters and an enhanced quality of filtered polymer. They are used in diverse kinds of spinpacks and for all major screenchangers brands. We offer a broad range of material for use as filling sands in the spinpacks such as stainless steel like Inconel , aluminium and more.

We are specialized in the development and production of porous metal filtration solutions. The use of filter media, elements and systems for industrial gas filtration, based on the special advantages of metal fibre media. The use of filter systems in the high temperature and corrosive, chemical and petrochemical process, for filtration of process and exhaust gases.

We offer an alternative in situations where high mechanical stability, long life, low pressure drop, easy cleaning and chemical and heat resistance are needed.

Depth filtration

Depth filtration is mainly used in applications where small dust loads are required to be separated from a gas stream. The contaminants are held in the multiple layer structure of the filter medium. Benefit from our depth filter systems that combine high temperature and corrosion resistance with high dirt retaining capacity and outstanding offline feasibilities, the ideal solution for your 

applications.

Advantages

High permeability, low pressure drop, large dirt holding capacity, long service life, easy to clean, reusable, compact structure, high porosity, pleatable, brittleness free, sintered and welded, fit for high temperatures and high pressure applications.

Applications

·         Purification of process gases to secure the downstream equipments

·         Catalyst protection

·         Ammonia and mixed gas filtration in nitric acid production

·         Purification of process gases such as hydrogen, nitrogen and oxygen

·         Steam filtration for pharmaceutical and food and beverage industry

How do mesh screens enhance the security level of your place

The mesh screen security products are vigorously tested to ensure they meet diverse industrial standards. They are subjected to extreme regime of impact tests and pull testing to ensure their inherent strength and structural integrity of the manufactured security product.

The screens are tested in general accordance when exposed to incident radiant heat achieving 41% reduction in the radiant heat flux between the inside and outside of the product.

In the areas prone to cyclones, the windows and doors are needed to be protected from flying debris. The security screens are tested to this standard. They are designed to replace existing window and door screens whilst securing your house or business against weather and crime. The screens look like an insect screen from a distance, they allow the breeze in while preventing the mosquitoes out. Although, they are unlike to any other screen you have ever seen, because they make your house virtually impenetrable.

The screen products offer large scale protection without looking like heavy duty system. With uninhibited views, while preventing the mosquitoes, the insect screens allow the breeze in without compromising the safety. The screens offer enormous strength against intrusion.

Made to protect from hurricane, the screens prevent the hassle of installing hurricane shutters. Our mesh screens qualify the four level testing in the industry standard. Installing mesh screens on your windows and doors significantly reduce the magnitude of heat entering your house, hence decreasing the need of air-conditioning, eventually the energy costs. When an insect screen is installed on your window system, it improves the window ability to restrict the solar radiation approximately by 52%.

Windows play a significant role in the construction of our house. They allow the entrance of light, control air supply and provide views to connect our internal living space with the outdoors. But the traditional windows can cause wide heat gain.

Safe window screens offered by insect screen supplier are static screens that can be installed in windows and doors of any style. They are unique and provide the window extensive strength against attack. The screens can be custom built that means a perfect fitting. So, the product can be custom made to fit the design and format of your windows. Heanjia supplies the mesh screens for the variety of window and door designs such as: Sliding windows, double hung windows, Louvers and lap louvers.

Our insect screens are a keyless exit system that allows you quickly exit in case of emergency but is hard to penetrate.

We offer security insect screens for doors of your house or business in standard frames, and even can be tailored. The screen fit easily in hinged or sliding doors. They feature the unique system for added security. The insect screens designed let you secure your area and make it fly and bug proof. They can be made from floor to ceiling length and can be bent to form a roof. They are a great way to make the best place in your house.

Decorative screens to protect and beautify your house or office

Heanjia offers screens for all who value the durability and reliability. All the windows are secured by tailored perforated stainless steel sun screens that also help to reduce energy consumption while filtering through the suitable magnitude of natural light. Critically this creates a suitable learning environment for people. Stainless steel is a reliable, durable and recyclable material, providing economical and sustainable solution.

Durable screens are for everyone who values the beautiful and innovative technologies and materials. We help you transform the ambitious architectural projects and your sentiments connected. We guide you through the benefits and practicality of your design. Using perforated sheets or expanded metals, we offer the best quality screens for use in large number of construction applications like car park, security screens, acoustic walls, ceilings, lighting, street furniture, balustrades and walkways.

Screens of decorative metal mesh perforated metals bring an exotic and modern twist to the architecture of any building. Perforated metals decrease the magnitude of direct sunlight to the open areas of the building. For the educational facility, it is essential for the architects to combine the best feasible indoor climate with an elegant exterior. Expanded metals are used to create decorative and versatile sun screens. To achieve more vibrant facade, two different types of expanded metal panels is used. It provides an interesting and light expression that is further improved.

For comfort and added privacy for a building, an architectural visor also scores highly on the environmental front. A common goals for the creators and developer of modern built environment, whether it is a business, educational establishment, shopping mall, try to conserve energy while decreasing the environmental footprint.

The inclusion of a perforated or expanded metal facade goes some way to fulfill this objective, stating that any cost involved in the configuration can be recouped as the heating and electricity bill decreases.

Considering a perforated sun screen on a building requires to meet specific standards. While stainless steel and copper can be used as the core material, a commonly used metal is aluminium.

Aluminum can be recycled easily, it is lightweight to install on a structure and needs nominal maintenance while meeting the environmental and sustainable needs, it can also be made cost-effectively.

An essential metal is the choice of finish that is applied, both longevity and aesthetic appeal. Different finishes can with benefit be used on perforated screens like anodizing, hot dip and electro galvanizing, and powder and wet coating.

Usually protection from extreme sunlight and adverse weather conditions while absorbing a limited magnitude of heat and light, sun screen can be the excellent combination of performance, innovation and sustainable design. The strength and beauty of a building with a durable perforated metal screen is that a climate controlled environment is developed, enabling right magnitude of natural light while conserving and deflecting the heat when required. Balanced magnitude of light and heat is received depending on the hole shape, open area of the perforation, angle, structure and mechanics of the sun screen, with raw material and finish.

Study of impact of mesh structure on electrolysis cells performance

Microbial electrolysis cells or MECs provide a high yield method for hydrogen production from different organic substrates, like wastewater and other biomass. Bacteria on the anode oxidize the organic matter and transform energy present in biodegradable substrate in current. With a small electrical input, hydrogen can be produced on the cathode under anoxic conditions, often with the help of a catalyst.

While diverse advancements in MEC performance have been made, creating an economical, scalable design is a critical challenge for the MEC to become a proven technology for hydrogen production. The cathode count be responsible for the maximum amount of total capital costs for the cells.

Nickel based alloys have shown a reliable electrocatalytic activity for the hydrogen production reaction in water electrolysis. Affordableand reliable mesh electrode made from stainless steel 304 with high nickel concentration is commercially available as an alternative to Nickel alloy. It shows good catalytic activation in an alkaline solution. In the neutral pH conditions, the maximum hydrogen production rate received was 1.7 m3 of H2/ m3 d and overall energy efficiency of 78% using the high surface area stainless steel 304 brushes at an applied voltage of 0.6V. It is better than that received with platinum-catalyzed flat carbon cloth cathode, showing that costly precious metals are not required. Although a widely complex structure of an MEC with brushes may limit this mechanism.

A linear sweep voltammetry is used to evaluate the current densities of various mesh and bubble properties were observed at different applied voltages.

Stainless steel mesh as in woven and expanded metal forms is used for its suitability as cathodes in Microbial electronic cells. Woven mesh and expanded mesh are expected to have effects on current densities due to bubble developed causing the difference between mesh functions. Both mesh forms have the same chemistry as of stainless steel 304 and are hence expected to have the same hydrogen production activation energies.

MECs are single-cell, cubic type reactors, they operate in fed-batch mode. To prevent gas accumulation between the mesh cathode and end plate on the top of the cylinder, a part of the top of mesh is cut and bent into the solution to ensure no loss in surface area.

Woven mesh shows higher increase in current as compare to expanded mesh. It is found that expanded produces current significantly lower than woven mesh at higher current density vales. Larger current per applied voltage of produced by mesh could introduce larger active surface areas than those estimated or different effects of structures on hydrogen bubble release. Depending on the outstanding performance of woven mesh, expanded mesh is not evaluated further.

Mesh configuration has significant impact on current. At low current density value, small hydrogen bubbles at low surface coverage occurs on the different mesh. With increase in applied current, the bubbles expand until their size is comparable to the mesh pore size. At the highest current density, the bubbles coalesce and quickly brake down from the surface, decreasing the overall bubble coverage.

Why sintered mesh screens are chosen over other filter media

High quality media is required for supreme quality filtration. Our mesh screens are used not only in the polymer filters and extruder screens, we produce the media for use in filters. Our fully integrated manufacturing techniques and technologies allow us to provide high performance filters at the reasonable price. Heanjia keeps a full range of tools to produce screens and filters for all types of screen changers.

Polymer industry is always in need of different types of filters to produce excellent quality resins. Tailored filters are required  to specific dimensions and requirement. The screen packs are made from a wide selection of alloys such as Nickel 200, Hastelloy, Monel and stainless steel grades. The screens are ultrasonically cleaned. The filtration components are produced for standard and custom resin production and compounding of resin.

Thousands of mesh specifications are produced for any specific micron ratings using multiple weave patterns. These patterns impact flow and filtration performance and have a significant contribution in deciding the screen performance, life and design.

Use of screen packs in plastic recycling

There are diverse styles of filtration products that are used in the plastic recycling industry. We can supply screens in all designs and patterns. We have specialization and potential to design supreme packs to aid in the following:

a.       Product throughput vs. filtration requirements

b.      Screen performance and cost

c.       Durable steels and nickel based high performance alloys are used

d.      Disc screens are used for mesh combination

e.      Screen packs are easy to handle

We fully understand the factors that impact your processing to provide mesh screens that perform at the desired levels at an economical price.

Polymer fibers and filaments

The polymeric fiber and monofilament production needs filters in different styles. We offer a complete range of screens for quality filtration.

Our woven mesh screens and fiber felt screens are fully controlled and tested. Sintered screen filter felts are ultrasonics cleaned.

Mesh screens for film filters

We understand the manufacturing processes for optical film and display films including strict quality control standards. We can produce filters that prevent any anomalies like carbon specs and gel left from melt stream. The long life sintered fiber felts are made to provide economical and unparallel services. We provide a wide array of auxiliary filtration components used in the polymer processing plants. The screens are made from various high performance alloys to provide necessary and optimal performance.

Screens for dryer filters

Keeping the dust particles away from the heat exchangers on drying equipment will increase the service life of your systems. Use of durable quality sintered filter media significantly improves the system performance as well as life.

With tailored design, the screens are used as a retrofit in any filter vessel. The productivity is significantly increased while maintaining the filter system. It saves the cost of vessels, tubesheets ad valves that would have otherwise made.

Materials for sintered mesh

The properties of the final component widely depend on the raw material used. Sintered wire mesh screens are made variety of alloys such as stainless steel, nickel based alloys, titanium and more.