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Kalamazoo Electropolishing Company
 
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Passivation of Stainless Steel

  • Complete Passivation Processing Line
  • Corrosion Prevention for all Stainless Steel Alloys
  • Chemical Cleaning Services for Removal of Oils & Residues from Machining, Forming & Welding

KEPCO has an entire line devoted to the passivation of stainless steel.  By passivating a metal surface, KEPCO removes the free oxides from the surface to insure a more passive and corrosion resistant surface.

KEPCO also offers a total cleaning service. Chemical cleaning leaves your stainless steel parts completely free of oils or residues left by forming, machining, welding or any number of other fabricating methods.

The Passivation Process

Passivation is performed to make a metal surface passive, i.e., a surface film is created that causes the surface to lose its chemical reactivity. Passivation unipotentializes the stainless steel with the oxygen absorbed by the metal surface, creating a monomolecular oxide film. Passivation can result in low corrosion rate of the metal.

Passivating Stainless-Steel Parts

A crucial step in maximizing the corrosion resistance of stainless-steel work pieces, passivation forms an extremely thin, protective oxide surface film. But it must be done properly.


Passivation of machined stainless-steel parts, correctly performed, maximizes corrosion resistance. Incorrectly performed, it can actually induce corrosion. Correct passivation can make the difference between premature failure and satisfactory performance. At the very least, it can be an insurance policy.


What exactly is passivation? It is simply a post-fabrication process that increases the resistance inherent in the particular grade of stainless steel from which the part was produced.


A clean, freshly machined stainless part automatically acquires this oxide film from exposure to oxygen in the atmosphere. In actual practice, however, contaminants such as shop dirt of particles of iron from cutting tools on the surface may reduce the effectiveness of natural film. When this happens, corrosive attack may begin.


The machining process itself can embed free iron into the surface of the part. A microscopic amount of metal, worn off the cutting tool, may be transferred to the stainless parts. Small particles of iron-containing shop dirt may also adhere to the stainless-steel surface. Though the metal may appear shiny in the asmachined condition, the invisible particles of free iron can cause a thin coating of rust to appear on the surface after exposure to the atmosphere. This is generally caused by corrosion of the tool steel and not the parent metal. Sometimes the crevice at the embedded tool steel particle or its corrosion precuts may cause attack of the part itself. These problems can be avoided by immersion in a passivating bath containing nitric acid that is capable of dissolving the tool steel (free iron).


Sulfides are another potential problem. They result from the addition of sulfer to free-machining stainless steels to increase machinability. Sulfides improve the alloy’s ability to form chips that break away cleanly from the cutting tool during the machining process. But unless the stainless steel is properly passivated, sulfides can form initiation sites for localized attack on the surface of the fabricated part. One purpose of passivating a sulfer-containing alloy is to remove sulfides present at the metal surface.


In both cases, passivating can achieve the overall objective-maximize the already inherent corrosion resistance of the stainless steel. A two-step procedure can provide the best possible corrosion resistance: (1) cleaning, a fundamental but sometimes overlooked operation; and (2) an acid bath, passivating treatment.

ON-SITE PASSIVATION SERVICES

KEPCO offers field services and can bring our 25 years of experience, service, and quality to your job site as if we were bringing our shop to you.  We take pride in our ability to work with the customer to achieve results and meet their deadline.

 

Our dedicated On-Site Team is experienced and thoroughly trained in the passivation field.  An On-Site Coordinator will implement the work plan following all federal, state, and site-specific safety regulations.  The Coordinator is the customer liaison for progress reports, paperwork, and general communications.

 

All On-Site Teams have completed all OSHA required training related to their work tasks.  On-going Safety Training programs insure a complete understanding of the requirements and possible hazards associated with their work environment.  KEPCO has an excellent safety record.

 

KEPCO's process meets or exceeds ASTM Industry Standards for passivation of stainless steel.  An approved test shall be performed and the results recorded to verify the passivation process has been completed.  Certifications will be forwarded to the customer after completion of work.  OurOn-Site passivation process provides maximum protection of stainless steel by providing:

 

  • Improved and faster removal of free iron from the surface
  • Low hazard chemistry 
  • Environmentally safe chemistry
  • Passivated surfaces that pass all salt spray, immersion and high humidity tests

 

KEPCO is committed to providing the highest standards of excellence to our On-Site Service customers through Total Team Involvement, Devotion to Quality, Assured Customer Satisfaction, and Competent Environment Stewardship.

 

Some of the On-Site services KEPCO offers are:

  • Alkaline Pre-Cleaning
  • Dry Ice Blast Cleaning
  • Rust Removal
  • Citric Acid Passivation (KEPCO On-Site citric acid cleaning and passivation process is based on new technology using safe and environmentally friendly citric acid to remove the free iron from the surface of stainless steel and chromium enrich the surface.)
  • Medical Grade Deionized Water Post Cleaning
  • Copper Sulfate Testing
  • Ferroxyl Testing
  • Conductivity Testing
  • Certifications of Conformity
  • On-Site Consultations

 

DESCALING OR DEOXIDIZING

TO REMOVE       

  • RUST
  • WELDSCALE
  • HEAT-TREAT SCALE
  • HEAT EFFECTS FROM:
    • BENDING
    • STAMPING
    • MACHINING
    • MECHANICAL PREPARATION

ACID DESCALING

Acid descaling refers to the use of an acid bath to remove weld discoloration, heat treat residues, rust, or other surface oxides. In general, these undesirable films must be chemically dissolved by the bath, and the time, temperature, choice of acid, and concentration may be dependent upon the nature of the scale. 

 


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