Category: Blog

What is Mechanical Polishing?

Mechanical polishing is the mechanical smoothing and removal of contaminants. It involves grinding, polishing and buffing of the surface. This process is used to smooth welds, prepare metal for surface treatments like electropolishing or provide a surface with a specified roughness.

What is Electropolishing?

Electropolishing is an electrochemical process that smooths the surface by removing the peaks on a nanoscopic level (anodic leveling). This enhances the corrosion resistance of austenitic stainless steels. And in some applications also reduces product adhesion and contamination buildup. Electropolishing may also be used for deburring and dulling sharp edges. The result is often a lustrous and reflective finish.

What is the difference between Mechanical Polishing and Electropolishing?

The differences between electropolishing and mechanical polishing may not be obvious to the unaided human eye, particularly if both surfaces are polished to the same micro-inch surface finish. The merits of electropolished surfaces become apparent, however, when viewed under high magnification.

Unlike electropolishing, mechanical polishing can distort the surface, leaving smears, cavities and torn metal. These cracks and crevices are huge contamination traps which limit the overall cleanability of a metal surface. These imperfections are often beyond the reach of aggressive ultra-cleansing applications. Even very fine mechanical polishing or buffing produce an abundance of scratches and strains in the metal surface. Moreover, a host of microscopic debris and abrasives can become embedded in the surface of mechanically polished metals.

Mechanical Polishing	Electropolishing
Smooth with abrasives	Smooth by anodic leveling
May increase product adhesion depending upon final grit size	Reduces product adhesion
May require more intensive cleaning process	Increases cleanability
High luster possible after labor intensive processing	High luster and reflectability typical in most stainless steel materials
Metal surface distortion is possible	Reveals the original crystal structure of the metal surface without distortion
May create microscopic scratches, stain the surface, embed abrasive residue	Completely smooths the metal surface and removes any contamination
High luster may require days to achieve	High luster often achieved in minutes

So why use one process over the other?

In many cases, electropolishing is best used to compliment mechanical polishing. Electropolishing operates in the micro range, smoothing and leveling defects to a few thousandths of an inch in depth. Larger defects may never be removed by electropolishing, warranting a mechanical prefinishing step to the complete process.

Electropolishing may improve the Ra value of a part by up to 50 percent. To lower the Ra finish, you may need to add mechanical pre-polishing before moving on to microfinishing with electropolishing.

Allegheny Surface Technology (AST) employs experienced and highly skilled craftsmen who have the training to perform this service at any facility. Our state of the art polishing facility and equipment enable us to consistently achieve your surface finishing requirements, as fine as single digit Ra readings with proper prefinshing. We are able to work on OEM parts as well as refurbish used vessels and equipment in our shop and customer locations with our field service technicians.

Manufacturing stainless steel parts begins with fabrication or machining. All parts must be made to particular specifications and follow the guidelines of design and application. Once fabrication or machining is complete, parts are likely to have with free iron and other foreign material embedded in the surface.

Why it matters: As the final step, passivation is crucial because it ensures the corrosion resistance of stainless steel parts. The successful establishment of corrosion resistance on a critical part ensures long, efficient service of the part or vessel in whatever process it’s used in. Whereas failure to do this correctly leads to corrosion, reduced efficiency and ultimately, reduced lifespan of the part. Altogether, these factors can increase costs significantly.

What is Passivation?

Passivation is a combination process – part cleaning and part protective – that creates a passive layer on a stainless steel surface. This layer protects the metal from selective oxidation or corrosion.

Specifically, passivation is a chemical process involving a mild oxidant, such as a nitric acid solution, that removes “exogenous iron or iron compounds from the surface of stainless steel by means of a chemical dissolution…that will remove the surface contamination, but will not significantly affect the stainless steel itself…for the purpose of enhancing the spontaneous formation of the protective passive film,” according to ASTM A380.

The passivation process removes what’s known as “free iron” contamination. While this contamination is a normal in the machining and fabricating process for any stainless steel part, such contamination areas are also potential corrosion sites. If left in place, they will result in premature corrosion and deterioration of the part.

This is where the passivation process as a finishing step – or a routine maintenance step – becomes critical to the life and usefulness of every stainless steel part.

Why is Passivation Necessary?

Our customers will often ask if passivation is necessary. If the interest is in achieving the longest life and the best operation of a component in a manufacturing process, the answer is “yes.”

Even though the definition of passivation focuses on removing the “free iron” contamination, stainless steel components typically also acquire areas of grease, oil, and other substances on their surfaces during manufacturing.  Moreover, microscopic particles of shop dirt or iron from cutting tools can become embedded in the surface of the stainless steel parts during machining. These foreign particles impair the integrity of the original protective layer. Passivation cleans away these contaminants and creates the necessary passive layer, providing the best possible corrosion resistance.

How is Stainless Steel Passivation Done?

The first step of the passivation process involves cleaning the parts to prepare them for the solution. This step removes grease, dirt, dust and other surface contaminants.

Then comes the oxidizer or “acid dip” stage. Each job is different. So success at this stage requires deep knowledge of the chemistry of the acid mixture and other aspects of the process. These include which acid recipe works best for each situation, the ideal temperature, optimum duration of the bath, and how to adjust each of these factors based on the materials treated. When all of these factors are aligned into an ideal process, all free iron is removed from the surface, allowing the formation of an evenly-distributed oxide layer.

A thorough rinse in clean water is the final step.

How is Passivation Validated?

Ensuring a successful stainless steel passivation process is achieved through testing and validation.

This final step assures the effectiveness of the passivation process and most importantly, certifies compliance with ASTM, Mil-Spec, and other industry standards.

When additional assurance is required for specific processes, parts are further tested using methods such as high humidity, salt spray, water immersion, and ferroxyl testing. Such measures are particularly important for complex, highly-regulated industries and applications like aerospace, medical, military, and other areas where high reliability or safety are critical.

Is Passivation a One-Time Only Process?

No. Parts need to be re-passivated as a part of routine maintenance, depending on the service of the part. Factors include the demands of its processing conditions and how aggressive the chemicals are for processing and cleaning. Remember: experts who specialize in passivation are your best guide in helping you assess the best process for the specific needs of your parts – and your process.

Allegheny Surface Technology is an industry leader in passivation services, delivering high quality services to our customers. Request a quote or call us to speak to a specialist about stainless steel passivation today.

Pickling and passivation are different types of chemical metal finishing that provide corrosion protection on metal surfaces. Both processes remove excess (or exogenous) iron or oxidation from the surface of whatever metal undergoes the process. Pickling (removing an oxide layer) and passivation (applying an oxide layer) are different finishing processes.

Why it matters: In order to achieve the desired results, it’s important to understand that pickling is a preparatory process, while passivation is a finishing process.

What is Pickling?

Pickling, also known as chemical descaling, is the chemical cleaning of metallic surfaces to remove impurities, stains or weld scale. This is done with an acidic solution. Allegheny Surface Technology uses pickling solutions containing nitric and hydrofluoric acids to remove weld scale and underlying chromium-depleted layers of a metallic surface, in order to restore the corrosion resistance of stainless steel.

Pickling is one of several possible pretreatment steps in other processing, such as passivation or electropolishing. Pickling is also useful as a superior cleaning operation on welded structures. The most commonly referred standard for pickling stainless steel is ASTM A 380, Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment and Systems.

What is Passivation?

Passivation is the chemical process (also involving an acid) that removes “free iron” from the surface of stainless steel, enhancing corrosion resistance of the metal. Passivation forms a chromium rich surface, as an invisible, inert (or “passive”) oxide layer when exposed to an oxygen-containing environment, such as air. The most widely used standards for passivating stainless steel are ASTM A967, AMS 2700, and ASTM A380.

What is the difference between Pickling and Passivation?

Pickling	Passivation
Pickling is a cleaning process.	A cleaning step is required before passivation.
Removes surface iron contamination, weld scale and heat tint from the surface.	Removes free iron contamination from the surface.
Uses acids that take off the surface of the metal to treat impurities on an atomic level.	Uses mineral or organic acids like either nitric acid or citric acid which are not as aggressive as the acids used in pickling.
Leaves a greater change to the metal. Leave a uniform matte finish.	Does not change the appearance or properties of the metal.

Passivation and pickling are often used as companion processes to remove contaminants and oxidation. Together, they improve corrosion resistance, thereby extending both the life and overall value of your stainless steel components.

Allegheny Surface Technology has metal finishing experts who will assist you in deciding which choice is the best for your stainless steel finishing needs.

The statement, “no job is complete without the proper documentation” holds true for many industries, as well as the organization overseeing them. The higher the operational standards, the more critical it is to document that procedures have been performed to meet or exceed those standards.

Most bio-pharma, food and beverage, cosmetics, and medical device manufacturers companies work closely with the FDA and USDA to develop procedures that ensure compliance with Current Good Manufacturing Practice (CGMP) regulations. When these procedures become a part of manufacturing practice, each step must be recorded and approved in real-time. If a facility is unable to “show its work” in a particular process, it’s very likely that the process will need to be performed again. This obviously costs time and money.

Consider this hypothetical example, where insufficient process documentation can lead to lost production time and reduced profits.

‘Henry receives a phone call from a customer who needs some parts electropolished. Unsure what electropolihing is, he looks online and finds a service provider that specializes in electropolishing. He receives a reasonable quote and sends out the parts to be processed. While waiting for the job to be completed, Henry researches electropolishing and develops certain expectations of what he can expect when his parts return. The parts are completed and returned on time. Henry inspects them and is pleased with results. He sends them on to his customer and, within a few days, receives an unexpected phone call in return. Unfortunately, his customer is not very happy and requests documentation detailing how these parts were processed. Henry is at a bit of a loss. He doesn’t have what his customer is asking for. He soon learns that without proper certification, the parts can’t be used and the process must be performed over again.’

Don’t be like Henry.

Quality documentation is too-often overlooked and missing, incomplete, inaccurate, or poorly-detailed certifications can lead to delays in product shipment or worse, products that must be reprocessed in order to fulfill a customer’s requirements.

The most reliable way to prevent such an unfortunate occurrence is to always request a sample of the certification provided for any requested process. A quality certification should be included with all processed parts with the following details:

Electropolishing

vendor’s company

owner/user’s name

description of component(s)

identification of the electropolishing procedure used

final surface finish report (Ra if required by the owner/user)

 

Passivation

owner/user’s name

description of system or component(s)

service provider’s company name

qualified passivation method used

documentation of passivation process, as follows: (1) written qualified procedure (2) documentation of process control of essential variables (3) instrument calibration records (4) certificates of analysis of all chemicals used (5) process testing and verification

postpassivation verification method(s) used

for material manufacturers/suppliers of components whose surfaces have been electropolished and/or passivated, a Certificate of Compliance for Passivation and/or Electropolishing stating that standard industry practices, such as ASTM A967 or ASTM B912, as applicable, have been used. If required to demonstrate the effectiveness of their procedure by a method mutually agreed upon.

When the metal finishing services you trust meet ASME BPE standards, you can be confident that they implement best practices to increase the safety and reliability of your parts.

By choosing an electropolisher that meets or exceeds these standards, you can increase your parts’ safety, reliability and service life. Allegheny Surface Technology has experience providing metal finishing services for a variety of bioprocessing industries, and always adheres to ASME BPE specifications.

Most stainless steel service providers offer a variety of services within their core disciplines, but few are able to offer a complete line of services from A to Z. We often hear from our newest customers about the challenges they had in finding one provider that doesn’t simply specialize in one or two services, but can handle everything from  single refurbishment to a complex project involving equipment that can’t be torn down and sent off-site.

If you’ve dealt with this dynamic, you know that working with multiple service providers can often lead to problems with managing your project, hitting your delivery timelines or occasionally, with the equipment itself.

Working with a one-stop shop means that you have a single point of communication. This allows you to develop a consistent dialog and a reliable relationship that delivers high-quality, on-time component services with each engagement.

Conversely, working with multiple suppliers to accomplish the same thing adds layers of complexity. This can have significant knock-on effects that hamper the flow of your project, unnecessarily inflate your costs, introduce the risks of variability and uncertainty and potentially compromise the quality of your final results.

Consider:

1. The time, cost and inconvenience of creating multiple POs for various suppliers. Remember, your time costs money, too!
2. Fully vetting those suppliers to ensure they are properly-certified, and that they have a track record of delivering compliant (and safe) results
3. More suppliers on-site means more safety training, in addition to the time and resources that go along with it, on your part
4. Risk of delay in the event of accident, personnel issues or equipment failures that cascade through the remainder of the project
5. Risk of injury from personnel attempting to make up for lost time

Every business seeks to operate as efficiently as possible, either by saving time, improving efficiency, reducing production costs, or a combination of these things.

In simplest terms, it’s more efficient, faster, more cost-effective and safer for a single, highly-qualified and experienced provider – a one-stop shop – to manage your stainless steel refinishing projects, instead of coordinating them on your own. Moreover, coordinated project management through a single point-of contact means that you are able to improve your own personal efficiency, freeing you to concentrate on more critical aspects of your business.

By choosing Allegheny Surface Technology as your one-stop stainless steel service shop for all of your surface finishing needs, you get coordinated project management, in addition to turnkey services for electropolishing, passivation, pickling, mechanical polishing, and vessel or tank repair.  We pride ourselves on efficient and professional work habits, and we have a solid track record of delivering compliant, certified and safe results on-time. We are passionate about helping our customers find a better, faster, and higher overall value solution.

Experience the difference of working with a one-stop shop and request a quote for your project, today.

Your pressure rated vessel needs to be repaired to the required standards to ensure safe operation.  But, how can you be sure your vessel meets those standards when the repair is complete?  Ensuring an ASME Code Weld repair is completed in accordance with ASME Division I Section VIII Rules for Construction of Pressure Vessels requires several steps.

Let’s dig into the process. 

When you have a pressure rated vessel that requires modification – or in need of repair that includes welding – gathering the right information is the most important factor in getting the project moving correctly.

First, get the build drawings and the vessel’s U-1 Report. These essential elements include the necessary calculations that ensure its pressure rating won’t be compromised by the modification or repair.

Once an engineer completes any follow-up calculations, any replacement parts must also be tested prior to installation, in order to ensure the replacement parts are also up to standard.  Be sure that your replacement parts include a material test report (MTR) and that these reports are reviewed prior to installation.

Next, remove the broken unit or make the necessary modifications.  Once any replacement components have been welded into their required locations, polish the surface surrounding the repair to the finish specified in the original drawings.

If the equipment requires electropolish and passivation, a qualified surfacing finishing technician ensures both processes meet the required standard to complete the repairs and prepare the vessel for testing.

Finally, once the repairs, modifications and polishing are complete, test the equipment per the specifications from the U-1 Report. This test must be witnessed by an Authorized Inspector in order to meet ASME specifications.

Once the vessel passes all tests, the repair tag will be welded to the vessel and it is ready to be placed back into service.

Your choice in service providers is critical to success.

One of the most challenging factors in a project like this is retaining a service provider that can supply all of the necessary elements for a successful, standards-compliant repair or modification.

An Engineering Department, Certified Welders, a Mechanical Polishing crew to polish the final surface to the desired finish, in addition to a Surface Finishing crew to complete the electropolish and/or passivation requirements, are all essential.

It’s rare to find a single provider that can accomplish all of these steps. And yet, working with multiple providers can often lead to difficulty in resolving any issues, questions or concerns that might arise during the project.

Working with a single company,  qualified to complete the entire process from end-to-end, ensures that you have clear communication, accountability and consistent practices applied to your project. When it’s done, you have confidence the vessel is both safe and meets to the required standards when the testing is complete.

Testing your service provider’s qualifications

When selecting a provider, keep these details in mind:

• Drawing and the U-1 Report

The drawing must be reviewed to determine the design is adequate for the modifications or repairs requested.  The U-1 Report will give information not found on the drawing about the testing that was performed originally or any modifications that have been done since it was originally manufactured.

• Qualifying a Welder

The welder must be certified to weld the material (Stainless Steel) and qualified by ASME Division I Section IX Welding, Brazing, and Fusing Qualification.

• Electropolishing and Passivation

The work affected areas may require Electropolishing and/or Passivation. The area should be Electropolished according to ASTM B912 and Passivation according to ASTM A967 to ensure the desired finish and proper certifications.

• Testing of repair

The testing must be witnessed by an Authorized Inspector from The National Board of Boiler and Pressure Vessel Inspectors (NBBI)

• Welding the repair tag on the vessel

The repair tag is placed as close as possible to the area on the tank with the original tag with the serial number and National Board number when it is welded to the vessel.

Ensuring you have the right personnel performing the work to modify or repair a pressure vessel ensures your equipment is safe to perform as intended.

We all want our products to shine over the competition’s.  But, are you having trouble getting the best surface finish on your stainless steel equipment?  There are plenty of factors that can contribute to – or even prevent – finished surfaces from achieving the best possible finish or shine.

When parts processed in February, then the next order in July and a final order in November, it’s not unusual that their consistency and finish will noticeably vary. So, why do they look different?

Variables that contribute to consistency or uniformity while electropolishing include, amps, process time, fixture, position and electropolishing solution.  For instance:

• If amps are too low, the parts will have a dull or uneven finish; too many amps will cause micro pitting – also known as “orange peel” or ”frosting”.
  
• Process times vary depending on the size of the part, its thickness, and the configuration or shape of the part.
• While securing the part to the fixture in the same way every time seems like a simple matter, wear on the fixture itself can cause the current to arc, leaving a burn mark. Even something as simple as insufficient current flowing through the part will leave dull areas or a bullseye pattern in the center of the part.
  
• The layout of the fixture and the angle at which the part is positioned in the electropolishing solution can cause gassing. When gas bubbles form during the electropolishing process and run along the part, this prevents the electrolytic solution from making contact with the surface, creating an area of weakness that will not receive the full electropolishing process.
  
• Electropolishing solution can vary within an acceptable range. The interaction of the solution with the amps, process time and fixture can cause finish variation if not tightly controlled.

With this many variables, how can you ensure your parts will look great every time?  This is where a process control plan is critical to consistent results. When the amps, time, and fixture information are recorded, this helps ensure the same finish on every part, every time.

A second crucial area is the electropolishing solution. The solution must be examined by a chemist regularly and throughout the process. This ensures the solution remains within the ranges that are required to achieve the desired results.

When process control plans and proper chemistry are combined by an expert service provider, your products will shine above the competition with the desired finish every time.

Let’s talk about “rouge” (French for ‘red’) and I don’t mean the cosmetic term…

Rouging is a symptom of corrosion that occurs on stainless steel due to iron contamination.  Often unpredictable and imperfectly understood, the rouge is composed of corrosion products that include hydrogen and iron oxides in different states of oxidation.

Specific colors (or rouging) vary depending on the type of iron oxidation and is thought to be the result of a momentary deterioration within the passive surface. Another theory connects rouging to the interaction of passive layers that are high in chromium with water.  The resulting corrosion depends on the chemical composition of the steel and its operating environment.

There are fundamentally three types of rouging:

• • Type 1 – Red, Orange, Brown – This is the most common. Type 1 is rich in iron oxide with crystals forming on the surface of the metal. This type can be easily wiped off, but can also be dislodged while the product is being processed resulting in particulate contamination. These crystals start out at sizes smaller than a micron, but can easily grow to measure 100 microns (0.1mm).
  • Type 2 – Gold, Red, Brown – This type of forms at the site it is discovered, and if dislodged, it may reveal the bright surface of the stainless steel underneath. It is generally caused by the presence of chlorides in the water and it often appears on surfaces where the passive layer has become weak or where passivation was never performed.
  • Type 3 – Gray or Black – Also known as “scale” and dependent on the surface where it appears, this rouge is unique to high temperature, high purity steam systems, and is a form of magnetite. Type 3 typically gets darker as it grows and is formed by the iron interacting with hot water vapor binding with the oxygen to form a ferrous oxide, which gives it its black color, along with ferric oxide. When on a rough surface such as un-passivated, mechanically polished steels, it may appear loose and powdery. On a smooth surface, it can be shiny and is often detected when it appears on filters or autoclaved items.

There are various consequences from rouging that are a major concern including:

• Unsanitary finish on the surface of the metal – leading to contamination of the product being produced.
• Equipment malfunction – if left untreated, rouge can lead to structural damage of components or full even system failure.
• Process failure to meet specification – may lead to fines from government regulators.

Solution:

• Type 1 – This can simply be removed via a little ‘elbow grease’ and a specific non-abrasive chemical treatment then passivated for protection.
• Type 2 – It can be harder to remove than the similar-looking Type 1 rouge. It cannot simply be wiped off, but be treated with a de-rouging process. More severe cases may require chemical electropolishing to completely eliminate it from the surface. Regardless of the cleaning process used, the surface must be passivated afterward to restore the passive layer which will have been damaged by the rouge as well as the removal process.
• Type 3 – It may have a relatively high silica content which makes it more resistant to the usual chemical treatments. Often, more aggressive chemical treatments needed as well as mechanical polishing or electropolishing. Passivation is also an essential step to be taken after de-rouging.

These solutions can be completed by your maintenance team if they have the capabilities or through on-site service providers with mechanical polishing, electropolishing, and passivating capabilities.

New brewers, wineries, and distillers spend hundreds of thousands of dollars on brand new stainless steel equipment. Many don’t know about caring for and conditioning the new equipment and this could lead to many problems down the road. Your brand new stainless steel isn’t like a new car where you can just jump in and drive around. You have to do a few things to the metal before you start producing. You can make good batches now, but maybe in 5 to 10 years your stainless steel starts to corrode a bit due to the acidic environment. That hundred thousand dollar investment that you put into equipment just went down the drain and could cost you your business.

You want to take care of your stainless steel equipment and your investment. A good way of doing this is to clean and passivate the equipment. This will increase the longevity of the equipment and provide a more consistent product.

The first step after you purchase your new stainless steel equipment is to clean it. Next comes the passivation. Passivation is the chemical process that removes free iron from the surface of stainless steel for the purpose of enhancing corrosion resistance. Allegheny Surface Technology offers either citric or nitric acid passivation based on your specific requirements. Passivation creates a chromium-rich surface which can form an invisible inert (passive) oxide layer as soon as it is exposed to an oxygen-containing environment (air).

Passivation will not change the appearance of the stainless steel. Passivation will not cause any change to the surface roughness. To verify the effectiveness of the passivation, Allegheny Surface Technology typically performs ferroxyl testing to ensure a successful passivation.

Have more questions? Feel free to contact one of our Passivation specialists by calling (866) 266-9293, or Request a Quote right here on our website.

At Allegheny Surface Technology we meet standards set by the following to better satisfy the needs and expectations of our customers.

Electropolishing Specifications:

• ASTM B912 – Standard Specifications for Passivation of Stainless Steel Using Electropolishing
• ASME BPE – Bioprocessing Equipment

Passivation Specifications:

• ASTM A967 – Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts
• ASTM A380 – Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems
• QQ-P-35C – Federal Specification: Passivation Treatments for Corrosion-Resistant Steel (replaced by ASTM A967)
• ASTM B912 – Standard Specification for Passivation of Stainless Steel Using Electropolishing
• ASTM B600 – Standard Guide for Descaling and Cleaning Titanium and Titanium Alloy Surfaces

Have more questions? Feel free to contact one of our Standards specialists by calling (866) 266-9293, or Request a Quote right here on our website.

Stainless steel pickling is a metal surface treatment used to remove impurities, such as stains, inorganic contaminants, rust or scale from stainless steel. It is commonly used to remove oxide layers from welding and heat-treating.  A solution containing strong acids, is used to remove the surface impurities. Metal pickling or chemical descaling is but one of several pretreatment steps available for preparing an article for further processing such as passivation or electropolishing, or to perform a superior cleaning operation on welded structures.

Key business benefits of stainless steel pickling are as follows: Uses chemical solutions consisting of nitric and hydrofluoric acids to remove the scale and underlying chromium depleted layers to restore the corrosion resistance of stainless steel. Mechanical removal of those imperfections may leave abrasive material or other particles embedded in the surface and in some applications, mechanical polishing may be impractical. Metal pickling is considered the preferred solution for the restoration of the corrosion resistance in stainless steel. Pickling will further create a uniform dull finish on the workpiece.

Have more questions? Feel free to contact one of our Pickling specialists by calling (866) 266-9293, or Request a Quote right here on our website.

Stainless steel passivation is the chemical process that removes free iron from the surface of stainless steel for the purpose of enhancing corrosion resistance. Allegheny Surface Technology (AST) offers either citric or nitric acid passivation based on your specific requirements. Metal passivation is but one of several pretreatment steps available for preparing an article for further processing such as electropolishing, or to perform a superior cleaning operation on welded structures.

Passivation creates a chromium rich surface which can form an invisible inert (passive) oxide layer as soon as it is exposed to an oxygen-containing environment (air).

Passivation will not change the appearance of the stainless. If the stainless has been heat treated or welded, the resulting scale or discoloration must be removed by either abrasive methods or by pickling. Passivation will not cause any change to the surface roughness. To verify the effectiveness of the passivation, Allegheny Surface Technology applies saline, copper sulfate, and ferroxyl testing to ensure a successful passivation.

Have more questions? Feel free to contact one of our Passivation specialists by calling (866) 266-9293, or Request a Quote right here on our website.

Recently Allegheny Surface Technology performed critical services On-Site at two large Biotechnology companies. The services and benefits are as follows:

» AST performed de-rouging and passivation on exterior surfaces of the customer supplied stainless steel equipment. The work was performed on a variety of parts including tanks, mezzanines, skids systems, countertops, benches, etc.  These services help prevent any cross-contamination from the exterior of the equipment to get into the product being produced and prolong the life and visual appeal of the equipment.

» Mechanically polished and passivated the interior of a parts washer. This service prolongs the life of the equipment.

» Mechanical polished five tanks to remove scratches and returned the interior surface to a required 20Ra or less. This process was followed by electropolishing and citric passivation of all interior surfaces. These services brought the tanks back to a better standard for operation and allowed the customer to visually inspect abnormalities in the tanks.

» Multiple code weld repairs consisting of the following:

» A tank alteration project to modify a large 10,000-gallon WFI holding tank. The WFI tank alteration project consisted of adding seven different size ports to a pressure-rated tank with an insulated jacket, ports ranged from 2” up to 6”. The modifications to the WFI tank allowed a central distribution to the whole facility. The additional ports were necessary to add distribution loops.

» Hinge repair for a manway. The Hinge repair was to prevent the manway lid from breaking off and causing an injury. A stopper was also installed to prevent the lid from opening too far.

» Repaired a leak on an autoclave. The repair on the autoclave ensures the pressure in the steam jacket and the heat in the autoclave are easily maintained.

At Allegheny Surface Technology, we recognize the importance of these critical services to our customers. We are aware that this is a partnership that relies heavily on each other, and when executed to its fullest potential, will ensure a successful future for both parties.

Have more questions? Feel free to contact one of our On-Site specialists by calling (866) 266-9293, or Request a Quote right here on our website.

Mechanical polishing is the mechanical smoothing and removal of contaminants. It involves grinding, polishing and buffing of the surface. This process is used to smooth out welds, prepare metal surfaces for electropolishing or provide a surface with a specified roughness.  Allegheny Surface Technology (AST) employs experienced and highly skilled craftsmen who have the training and certification to perform this service at any facility.

Our state of the art polishing facility and equipment enable us to consistently achieve your surface requirements, as fine as single digit R_a readings. We are able to work on OEM parts as well as refurbished used vessels and equipment in-house and on-site. Allegheny Surface Technology can also perform compound – free mechanical polishing, a requirement in several pharmaceutical applications.

The techniques available are:

• Abrasive belt polishing
• Abrasive wheel polishing including nylon, flap and combination wheels
• Automated and hand polishing equipment
• Custom machinery for OD and ID polishing of tubular work pieces.

Electropolishing is an electrochemical process that smoothes the surface by removing the peaks on a nanoscopic level (anodic leveling). This enhances the corrosion resistance of austenitic stainless steels, and in some applications also reduces product adhesion and contamination buildup. Electropolishing may also be used for deburring and dulling sharp edges. The result is often a lustrous and reflective finish.

Which is better? Electropolishing:  The CLEAR advantage

Electropolishing typically creates a bright, smooth, and more highly corrosion resistant, sanitary finish. Other advantages of electropolishing include:

• Reducing the surface area on a microscopic level. This reduces product adhesion and contamination build-up, and cleaning can be performed more efficiently.
• Electropolishing has been proven to reduce bacterial biofilm build-up and the appearance of rouging.
• De-burring- The electropolishing process naturally has greater current densities at high points and less at low points. Due to the higher current densities at the high points, the burrs are removed at a much faster rate, leading to a smooth clean surface.
• Aesthetics- Through proper electropolishing, the microscopic surface becomes smooth and clean, containing a nickel-chromium enriched surface that results in a lustrous finish. This facilitates a visual inspection since any remaining imperfections will be magnified.

Have more questions? Feel free to contact one of our Mechanical Polishing & Electopolishing specialists by calling (866) 266-9293, or Request a Quote right here on our website.

Passivation of stainless steel is the chemical process that removes free iron from its surface for the purpose of enhancing corrosion resistance. Allegheny Surface Technology (AST) offers either citric or nitric acid passivation based on your specific requirements. Steel Passivation creates a chromium rich surface which can form an invisible inert (passive) oxide layer as soon as it is exposed to an oxygen-containing environment (air).

Stainless passivation will not change the appearance of the metal. If the stainless has been heat treated or welded, the resulting scale or discoloration must be removed by either abrasive methods or by pickling. When AST passivates stainless it will not cause any change to the surface roughness. To verify the effectiveness of the passivation process, Allegheny Surface Technology applies either saline or ferroxyl testing to ensure successful passivation. The highest form of passivation is electropolishing.

AST can handle almost any size and shape parts. If you can’t send it to us, we will come to you. We passivate vessels, pipes, tubing, manifolds, enclosures, frames, and architectural components, just to name a few. Have more questions? Feel free to contact one of our stainless passivation specialists by calling (866) 266-9293, or Request a Quote right here on our website.

Exceptional standards, customer service, and workmanship make all the difference.

Every discipline has its exemplars and its “wannabes”. But how do you tell the difference between them? Here are five useful indicators that can help you distinguish the cream of the crop in electropolishing companies from those for whom polishing stainless steel is not exactly a core discipline.

1. Customer service: You can tell a lot about a company by how they answer the phone when you call. Too often we’re greeted by auto-attendants, which possess all the personality and sensitivity of a sponge. When a company demonstrates from your very first contact that they care enough to invest in a real person to interact with you and get you what you need, that’s a strong indicator that customer service is among their top priorities.
2. Workmanship: Of course, you could be dealing with the nicest people on earth…who nevertheless lack the competence to do your job right. Now, we’re not saying that we’re the only ones who can properly electropolish your critical instruments and metal surfaces. But Allegheny Surface Technology has, over the course of decades, perfected its chemistry and electrical current distribution targets to exacting standards that result in consistent, repeatable results. In fact, our Process Control Plans allow us to reliably handle every job – for small parts or large vessels – either at our facility or at your site.
3. Quick turnaround: Electropolishing and other surface finishing methods are usually the last steps in a manufacturing process that may have been months or years in development. In our view, this means that quick turnaround is essential to completing the project on-time and within budget. We get it, and this is why Allegheny Surface boasts the capacity to run multiple electropolishing lines on all two shifts. This enables us to turn around most electropolishing projects (and most orders) in just 5-7 days.
4. Quality assurance: Three words: Quality Assurance Protocols. We look at this as an extension of our workmanship commitment, and we don’t just claim it; we guarantee it. Whether our electropolishing services are performed in our clean facility or on-site at your operation, our detailed procedures, stringent guidelines, and continuous monitoring ensure superior results. For more details, see our Quality Assurance page.
5. A superior level of commitment, and dedication to the end product: Okay. So maybe electropolishing steel isn’t the most glamorous thing in the world, but that’s no excuse to do a job that literally lacks luster, particularly when corrosion or a poor finish bleed money from your operation. Time after time and in project after project, Allegheny Surface Technology delivers electropolishing results that translate into superior aesthetics, cleanability, and process control.

Have more questions? Feel free to contact one of our electropolishing specialists by calling (866) 266-9293, or Request a Quote right here on our website.

If you came here looking for a brine or vinegar solution in which foods are preserved, this is not that kind pickling! This article is going to talk about the differences between pickling stainless steel vs electropolishing as a metal surface treatment. Ultimately, both processes are intended to enhance the available chromium material on the surface and promote the formation of chrome oxide, but their intended uses and results differ considerably.

In general, the pickling of stainless steel is the removal of oxide layers resulting from welding and heat-treating.  In particular, stainless steel pickling is a metal surface treatment used to remove impurities, such as stains, inorganic, contaminants, rust or scale from stainless steel, where a solution containing strong acids is used to chemically etch the surface of the material and preferentially remove iron molecules. Metal pickling or chemical descaling can be used solely or in conjunction with follow-up processes including passivation or electropolishing.

Allegheny Surface Technology uses pickling solutions consisting of nitric and hydrofluoric acids to remove the scale and underlying chromium depleted layers. This restores the corrosion resistance of stainless steel, whereas mechanical removal of those imperfections may leave abrasive material or other particles embedded in the surface. This makes mechanical polishing impractical for some applications. Metal pickling is considered the preferred solution for the restoration of the corrosion resistance in stainless steel and furthermore, creates a desirably-uniform matte finish on the workpiece, and utilized in a number of areas including oil field equipment, wastewater treatment facilities, and any marine environment.

By comparison, electropolishing may be preferred to metal pickling for some applications. In the electropolishing process, metal removal is achieved by applying electric current to a part submerged in an electrolytic bath. Unlike the dull finish of pickling, electropolishing typically creates a bright, smooth, and more highly corrosion resistant, sanitary finish. Other advantages of electropolishing include:

1) Reducing the surface area on a microscopic level. This reduces product adhesion and contamination build-up, and cleaning can be performed more efficiently.

2) Electropolishing has been proven to reduce bacterial biofilm build-up and the appearance of rouging.

3) De-burring- The electropolishing process naturally has greater current densities at high points and less at low points. Due to the higher current densities at the high points, the burrs are removed at a much faster rate, leading to a smooth clean surface.

4) Aesthetics- Through proper electropolishing, the microscopic surface becomes smooth and clean, containing a nickel-chromium enriched surface that results in a lustrous finish. This facilitates a visual inspection since any remaining imperfections will be magnified.

Have more questions? Feel free to contact one of our pickling specialists by calling (866) 266-9293, or Request a Quote right here on our website.