Aluminum Alloy Selection for Corrosion Resistance

The most common aluminum alloys used for flanges each offer different corrosion characteristics:

6061-T6:

• Excellent general corrosion resistance

• Good strength-to-weight ratio

• Widely available and cost-effective

• Performs well in atmospheric and freshwater exposure

• Vulnerable to certain chloride environments

5083:

• Superior saltwater corrosion resistance

• Excellent weldability

• Moderate strength

• Preferred for marine applications

• Less commonly available in standard flange configurations

7075:

• Highest strength aluminum alloy commonly used for flanges

• More limited corrosion resistance

• Requires careful surface treatment in corrosive environments

• Typically used where mechanical properties are paramount

• Generally more expensive than other aluminum options

Critical Surface Treatments

Raw aluminum flanges rarely provide optimal corrosion performance. Consider these surface treatment options:

Anodizing:

• Creates hard, protective oxide layer

• Available in various thicknesses and sealing options

• Can be colored for identification or aesthetic purposes

• Provides excellent abrasion resistance

• Type III (hard anodizing) offers superior protection

Conversion Coatings:

• Chromate and chromate-free options available

• Excellent base for paint systems

• Provides good electrical conductivity

• Typically thinner than anodized layers

• Often more economical than anodizing