Chromate Conversion Coating

Definition:
Chromate conversion, also known as chemical film, alodine or iridite, offers increased corrosion protection on aluminum. It is inexpensive, electrically conductive and is often used as a pre-treatment for paint and adhesives. Chromate can be used as a standalone finish or as a post treatment over other metal plating finishes.

Spec(s):
Mil-C-5541 or Mil-DTL-5541 or Mil-DTL-81706

Classifications:
Type I-Compositions containing hexavalent chromium
Type II-Compositions containing no hexavalent chromium
Class 1A-For maximum protection against corrosion, painted or unpainted
Class 3-For protection against corrosion where low electrical resistance is required

Spec(s):
ASTM B449-93 (re-approved 2015)

Classifications:
KEY: Class, Appearance, Coating mass per unit area g/m2, corrosion protection
1 – yellow to brown, 0.4 to 2, maximum corrosion resistance generally used as final finish
2 – colorless to yellow, 0.1 to 0.4, moderate corrosion resistance, used as a paint base and for bonding to rubber
3 – colorless, less then 0.1, decorative, slight corrosion resistance, low electrical contact resistance
4 – light green to green, 0.2 to 5, moderate corrosion resistance, used as a paint base and for bonding to rubber

Spec(s):
ASTM-B921-08 (reapproved 2013)

Classifications:
1 – Maximum corrosion resistance generally used as a final finish
2 – Moderate corrosion resistance, used as a paint base and for bonding to rubber
3 – Decorative, slight corrosion resistance, low electrical contact resistance
4 – Moderate corrosion resistance, used as a paint base and for bonding to rubber

Available Process(es):
Hand-line
Large Capacity Automated Hoist-line

Notes:
JMD can provide corrosion testing according to ASTM B117 per request.
JMD offers both RoHS compliant and non RoHS compliant chemical conversion coatings.