Tag Archives: Salt Spray

Corrosion resistance testing assess the impact of corrosive atmospheres on components, coatings, etc. Atmospheres are in general classified in to reductive, neutral, and oxidative atmosphere. Normal air which contains oxygen can be considered oxidative. Thus, some materials like iron will continue to rust and become oxidized if exposed to normal air for long period of time. Reductive atmosphere occurs in equipment like furnaces, internal combustion machines, etc.

Corrosion resistance testing can be classified in to pure corrosion and stress corrosion testing. In pure corrosion testing materials and components are exposed to only corrosive atmosphere to assess the reaction. Typical examples are rusting, hydration, etc. Buildings and structures suffer from simple corrosion attacks. Stress corrosion testing involves mechanical forces in addition to corrosive atmosphere. Power generation equipment like boilers suffer from mechanical forces in addition to corrosion. These mechanical forces are variable, thus leading to a combination of corrosion and fatigue. Often equipment like gas, steam turbines, etc., operate at high temperatures. Corrosion in these cases is augmented by mechanical loading at high temperatures. In extreme cases like nuclear power generators, materials suffer from irradiation from neutrons, and other sub atomic particles in addition to mechanical forces and corrosion. Some known corrosion tests are CASS, NAWLT, EXCO, etc.

Capability – At TTL, we test components and coatings for a variety of customers from aerospace, automotive, truck OEMs as well as mining, metals, and coating manufacturing markets. We have several environmental cabinets to run salt spray, salt fog, acidified salt spray, etc., on small test coupons to full sized components like truck wheels, auto wheels, etc. In addition, we have specialized fixtures for stress corrosion testing of material coupons. We have also environmental cells for testing corrosion fatigue, which is generally carried out in a regular tensile test frame under tension or flexure mode. The cells have capability also to run at higher or lower temperatures if required.

Some relevant standards:

• ASTM A961 – Standard Specification for Common Requirements for Steel Flanges, Forged Fittings, Valves, and Parts for Piping Applications
• ASTM B117 – Standard Practice for Operating Salt Spray (Fog) Apparatus
• ASTM B368 – Standard Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)
• ASTM G34 – Standard Test Method for Exfoliation Corrosion Susceptibility in 2XXX and 7XXX Series Aluminum Alloys (EXCO Test)
• ASTM G36 – Standard Practice for Evaluating Stress-Corrosion-Cracking Resistance of Metals and Alloys in a Boiling Magnesium Chloride Solution
• ASTM G37 – Use of Mattsson’s Solution to Evaluate SCC Susceptibility of Copper Zinc Alloys
• ASTM G47 – Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• ASTM G67 – Standard Test Method for Determining the Susceptibility to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid (NAMLT Test)
• ASTM G85 – Standard Practice for Modified Salt Spray (Fog) Testing
• ASTM G103 – Standard Practice for Evaluating Stress-Corrosion Cracking Resistance of Low Copper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6% Sodium Chloride Solution
• ASTM G110 – Standard Practice for Evaluating Intergranular Corrosion Resistance of Heat Treatable Aluminum Alloys by Immersion in Sodium Chloride + Hydrogen Peroxide Solution
• ASTM G112 – Standard Guide for Conducting Exfoliation Corrosion Tests in Aluminum Alloys
• ASTM G123 – Standard Test Method for Evaluating Stress-Corrosion Cracking of Stainless Alloys with Different Nickel Content in Boiling Acidified Sodium Chloride Solution