Understanding AMS 2700: The Aerospace Industry Passivation Gold Standard
What is AMS 2700?
In aerospace manufacturing, a microscopic surface defect can lead to catastrophic failure. Whether you’re using steel parts for planes, rockets, or something in between, keeping stainless steel parts up to code is vital in this high-stakes industry.
AMS 2700 (Aerospace Material Specification) is the gold standard for this essential process. Maintained and updated by SAE International, a global association and standards development organization, the AMS 2700 document details the requirements for passivation. Passivation on stainless steel removes free iron and contaminants to form a protective oxide layer against corrosion.
Why is the AMS 2700 standard important?
AMS 2700 ensures that stainless steel components manufactured all over the world remain reliable. A stainless steel part made in California may end up welded to another piece made in Ohio. For this reason, it’s vital that all components of all origins are properly passivated to the same standard.
Breaking Down the AMS 2700
The AMS 2700 standard gives manufacturers two methods for passivation and multiple avenues for testing:
The Methods
Method 1- Nitric Acid
Using nitric acid is the more traditional approach to passivation, but it may require the use of hazardous, toxic material which necessitates environmental compliance and strict safety protocols.
The AMS 2700 breaks down nitric acid passivation into 8 different “Types.” Each Type specifies different temperatures to passivate at, as well as immersion times and proper chemistry solutions.
Method 2 – Citric Acid
This method is a more modern, environmentally friendly choice. Many industries are moving toward citric acid passivation as a way to keep workers safer, dispose of byproduct waste more easily, and target free iron as effectively as possible.
The Classes
AMS 2700 details how often a part should be tested for effective passivation. Depending on which class the part belongs to, it will be assigned a specific testing frequency.
- Class 1: Testing not defined or as specified by the customer.
- Class 2: Testing is one part per lot.
- Class 3: Testing should occur on a periodic basis.
- Class 4: Testing frequency is defined by a 4.3.4 sampling plan.
The Passivation Process According to AMS 2700
Step 1: Pre-Cleaning
It is vital to clean stainless steel before passivation to ensure that the entire surface is free of contaminants. You cannot passivate a surface that’s covered by residue, oil, or contaminating particles. This could cause spotty passivation and jeopardize your parts.
Step 2: Select Your Method
Choose between nitric and citric passivation. If nitric passivation is chosen, you must match the correct “Type” to the material you are passivating. Reference the AMS 2700 to avoid using the wrong temperature and chemistry.
Step 3: The Passivation Bath
With the correct temperature, amount of time, and chemistry solution, you will achieve an optimal passivation bath for your stainless steel. If the bath specs are incorrect, the protective oxide layer may not form correctly.
Step 4: Rinsing
The nitric or citric acid must be neutralized to end the chemical reaction, allowing the oxide layer to form. Deionized water or Reverse Osmosis water are commonly used in this rinsing phase to prevent contamination.
Step 5: Verification Testing
Stainless steel parts will be tested based on the frequency and standard of their assigned Class. Testing methods include but are not limited to:
- The Water Immersion Test: Submerging parts to check for rusting.
- The High Humidity Test: Exposing parts to moisture.
- The Salt Spray Test: A common accelerated corrosion test.
- The Copper Sulfate Test: A test that turns pink if free iron is still present.
Partner With the Experts
If you’re looking for more information about the AMS 2700 standards or passivation, our team at JAYCO Chemical Solutions can help. Explore our products or schedule a consultation today.
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