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How To: Passivation for Stainless Steel Vessels

How To: Passivation for Stainless Steel Vessels How To: Passivation for Stainless Steel Vessels How To: Passivation for Stainless Steel Vessels How To: Passivation for Stainless Steel Vessels


Rapid data center expansion and modern HVAC demands have led more engineers and specifiers to choose stainless steel vessels for their systems. But what exactly is passivation, and what makes a passivated stainless steel vessel desirable over traditional carbon steel?

What is Passivation?

Passivation is a multi-step chemical finishing process performed after components are manufactured, welded, and assembled. Its primary goal is to maximize the steel’s natural corrosion resistance.

There is a common misconception that passivation physically fills surface flaws or mechanically alters the strength of the metal. In reality, it works chemically: during fabrication processes like cutting, machining, and welding, microscopic traces of free iron (tramp metal) from tooling get embedded into the steel’s surface. If left untreated, these iron particles react with air and moisture, triggering localized rust, pitting, and long-term surface deterioration.

Passivation removes these iron contaminants, allowing the stainless steel to protect itself as intended.

How Passivation Works: Building the Oxide Layer

Stainless steel owes its corrosion resistance to chromium ( of the alloy). When an acid bath selectively dissolves surface iron, it exposes an enriched concentration of chromium underneath.

Once rinsed and exposed to ambient air, this chromium rapidly reacts with oxygen to form an imperceptibly thin, continuous, and self-healing chromium oxide passive layer. This layer acts as a permanent barrier between the raw steel and the surrounding environment, keeping moisture and corrosive agents out.

Choosing the Acid Chemistry: Nitric vs. Citric

Passivation typically relies on one of two acid types:

The 4-Step Passivation Process

Achieving a true passive finish requires a tightly controlled sequence:

  1. Pre-Cleaning & Degreasing: Oils, machining coolants, and shop dirt are washed away. Acid cannot dissolve free iron if organic residues block direct contact with the metal.
  2. Acid Bath Immersion: The vessel is submerged in a controlled nitric or citric acid bath to dissolve free iron and surface contaminants.
  3. High-Purity Rinsing: The part is thoroughly rinsed with clean water to flush away acid residue and prevent chemical staining.
  4. Air Drying & Passive Layer Formation: As the vessel air-dries, exposed surface chromium reacts with ambient oxygen to form the protective chromium oxide film.

Why Passivation Is Exclusive to Stainless Steel

Passivation can only be performed on stainless steel and compatible high-chromium alloys. Carbon steel lacks the chromium required to build a protective oxide layer. If you submerge carbon steel into a passivating acid bath, the acid will aggressively etch and eat through the raw iron, weakening the vessel rather than protecting it. Carbon steel must instead rely on internal coatings, linings, or chemical system inhibitors for corrosion protection.

Stainless Steel Solutions from Wessels Company

By removing surface contaminants and enabling full passive oxide film growth, passivation ensures stainless steel vessels stand up to the most strenuous and harsh operating conditions.

Wessels Company offers passivation options across our stainless-steel product lines, including expansion tanks, thermal energy storage vessels, and air-dirt separators. In addition, some sourcing partners offer ferrous-free facilities to prevent cross-contamination. For more information on custom stainless steel vessel options or to request a quote, visit westank.com or call our headquarters at 317-888-9800.

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How To: Punch an Expansion Tank Bladder Hole

How To: Punch an Expansion Tank Bladder Hole

Wessels Company offers replacement bladders for our line of removable bladder expansion tanks. The butyl bladders come with a standard hole in the bottom of the bladder, but sometimes a larger-sized hole is recommended for optimal installation.

Wessels manually punches bladder holes to the correct size. However, if a bladder you receive needs modification, you can follow these easy steps to correctly expand the connection opening. The size of the hole will depend on the size of the tank.

Tank Size:                                          Hole for connection:
85 – 130 liters                                    1 inch
200-400 liters                                    1 ½ inch
400+ liters                                         2 inch

Be sure to carefully remove the bottom system connection and use the inside lip to trace a hole centered around the pre-punched hole at the base of the bladder.

The hole can be expanded with either a leather punch or carefully cut with a pair of very sharp shears (gardening shears will work). If using shears, cut along the traced line from the previous step.

WARNING: If the bladder tears or is not cut based on the interior lip of the bottom system connection, the connection will be unable to seal and the bladder will not work properly.

If using a leather punch, make sure it is the correct diameter. Once the correct punch is secured, place a piece of wood large enough to cover the entire hole into the bladder. Place the pre-punched hole over the wood and center the leather punch on top of the bladder hole. Strike the handle of the punch with a mallet until the metal of the leather punch punctures the wood and cuts cleanly through the butyl.

Once the hole is cut, replace the bottom connection, and replace the bladder.

For instructions on replacing a bladder, watch the Step-by-Step Guide Video on Youtube or reference the installation manual.

Please contact the warehouse at 317-888-9800 for more technical information on bladders or hole punching.

May Employee Spotlight Noah Barrow

May Employee Spotlight Noah Barrow

We are happy to welcome the newest member of the Wessels Company family, Noah Barrow.  Noah became Purchasing Manager in April of 2023.  Noah attended Indiana University and is a life-long Indiana Pacers fan.  He also played in a band and taught English in Japan for 5 years.  Noah enjoys singing, playing guitar, shooting 3-pointers, traveling, and exploring new places in his spare time.  We are incredibly happy to welcome Noah to Wessels.

Noah fast facts:
Favorite color: Blue
Favorite food: Pizza & Long’s donuts
Likes: Playing guitar and hiking
Roots for the Indiana Pacers

Noah Barrow
Purchasing Manager
(317) 888-9800 ext.
[email protected]

Pricing Correction for 2023 List Price Book

Pricing Correction for 2023 List Price Book

March 2023

Wessels Company
101 Tank Street
Greenwood, IN 46143

Subject: PRICING CORRECTION

Dear Customer,

In the January 2023 print version of Wessels Company’s List Price Book, an error incorrectly listed the prices of the FX100V and FX200V. The correct pricing should be:

FX100V: $1,006.00
FX200V: $1,555.00

We apologize for any inconvenience. For the most up-to-date pricing, lead times, new products, and discounts, please visit www.wesselsvessels.com.

Wessels Condensate Neutralizer

Wessels Condensate Neutralizer

WCNWessels Condensate Neutralizers (WCN) neutralize condensate issued by modulating condensing gas heating devices. A rigid pipe links the heating device to the WCN unit to treat the condensate. The media in the unit neutralizes the condensate pH to make it safe for building components and the environment. WCN units can contain up to three media bags to suit different heating device capacities and treatment condensate volumes. Media bags have a label to mark the installation date. Up to 3 WCN-2 units can be combined with connectors.

Download brochure

Download submittal

Employee Spotlight: Rem Mawi

Employee Spotlight: Rem Mawi

Please welcome one of the newest smiling faces at Wessels Company: Rem Mawi (pronounced M-oy). Mawi joined the Accounts Payable department in September 2022. Her favorite part of the job is organizing. Mawi likes teaching, sports, cars, and fashion. Her hobbies include cooking, singing, drawing, and sewing. She is a polyglot fluent in 3 different languages: English, Burmese, and Hakha. Mawi is a soccer fan and during soccer season she can be found rooting for Manchester United. We are very happy to welcome Mawi to the Wessels family.

Mawi Fast Facts:
Preferred name: Mawi
Favorite food: Asian cuisine
Likes: Sports, cars, and fashion

Rem Mawi
Accountants Payable
e-mail: [email protected]
phone: 317-888-9800 ext. 1014

Press Release: New All-in-One Multi-Purpose Tank Series

Press Release: New All-in-One Multi-Purpose Tank Series

PRESS RELEASE

February 2023
Contact: Rebecca Bennett- Marketing Coordinator
[email protected]
317-888-9800
For Immediate Release

Wessels Announces New All-in-One Multi-Purpose Tank Series

 

GREENWOOD, IND. – Wessels Company has brought to market the new WMT Series multi-purpose tank. This all-in-one tank can be used as a primary/secondary hydraulic separator, air and dirt eliminator, and buffer storage for either hot or chilled water systems.

The innovative design incorporates a buffer volume that slows fluid velocity resulting in superior air elimination. Air and dirt elimination efficiency are also greatly increased with the introduction of the highly customizable WesPro Super Filter Baffle System, a patented coalescing media available in eight different internal configurations.

Inlet and outlet ports can be manufactured anywhere between 90° and 180° apart, depending on need, with flanged, NPT, or grooved connections available. Wessels has upped the ante by also offering several optional upgrades. Along with new spray-on insulation, jacketed WesFoam insulation, or air vent trim package, the WMT differentiates itself from other multi-purpose tanks by being compatible with the Wessels WesMag magnetic filtration system. With WesMag, ferrous particulate can be caught and removed, increasing the life of system components.

A new brochure and easy-to-use all-in-one submittal for the new WMT can be found online.

For more information, pricing, and availability, call 317-888-9800 or visit the WMT product page. Coming to wesselsvessels.com soon.

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JAN 1, 2023 LIST PRICE INCREASE NOTICE

JAN 1, 2023 LIST PRICE INCREASE NOTICE

Wessels Company
101 Tank Street
Greenwood, IN 46143

Subject: 2023 PRICING NOTICE AND NEW CATALOG

Please consider this memo full notice:

January 1st, 2023, the Wessels product catalog will see a List Price Increase.

The new year is approaching, which means work on the 2023 list price product catalog has begun. Wessels remains dedicated to offering competitive pricing for our wide range of product offerings, which will include new small, large, and high connection cold water buffer tanks, multi-purpose tanks, innovative degasser accessories, and new smart tank control and measuring devices.

Wessels continues to offer pioneering product lines like the Rx and Full-Flow thermal expansion tanks, which use mixing and antimicrobial plating to combat the growth of biohazardous bacteria, and WesMag Filtration adaptations that drastically increase the life of filtration vessels, air and dirt separators, and other HVAC and plumbing equipment.

We will have more details about these price changes in the weeks to come. Wessels will continue to honor 2022 pricing until January. We’re also happy to announce we are extending our 3% discount on orders placed through our e-shop wesselsvessels.com into 2023. As always, we thank you for your continued business and look forward to forging ahead together in the new year.

Sincerely,

Wessels Company

Employee Spotlight: Mike Goshen

Employee Spotlight: Mike Goshen

December Employee Spotlight

One of the newest team members at Wessels is Design Engineer, Mike Goshen.  Mike has been in the Engineering department for about 2 months. He is currently working full time and attending classes to attain an electrical engineering degree.  In his spare time, he likes spending time with his wife, watching movies and working out. Mike likes to travel and he and his wife are trying to visit all 50 states.  In his free time he can be found watching UFC and keeping busy with his 5 pets: three dogs and two cats.  Please help us in welcoming Mike to Wessels!

 

Mike fast facts:

Interesting fact: he’s ambidextrous

Hobbies: working out, golf and electronics repair

Future plans: he wants to learn sign language and to ride a motorcycle.