Metal complex dyes are known as pre-metalized dyes that show a great affinity towards protein fibers. Commonly metal complex dye is Chromium or Cobalt complexes. One of the popular metal complex dyes is 1:2 metal-complex dyes that find application for dyeing polyamide fibers. 

Metal complex dye is used for a variety of applications. The main application is dying the materials like stationery printing inks, wood stains, leather finishing, inks, and coloring for plastics and metals. Highly effective anticorrosive pigments are best suited to direct-to-metal, industrial or automotive coating for metal applications. Metal complex dyes are the most favored for dyeing wool. 

Excellent Features of Metal Complex Dyes:

· Light-fastness

· Medium washing fastness

· Shows very good penetration characteristics and level dyeing

· Shows excellent cover up for the irregularities in the substrates

Metal complex dye is used in pH conditions, when applied in the dying process that is regulated by user class and the type of fiber like wool, polyamide, etc. For the fiber like wool the pH levels typically range from:

· Strongly acidic -ranges from 1.8–4 for 1:1 metal complex dye

· Moderately acidic neutral — ranges from 4–7 for 1:2 metal-complex dyes

The dye molecules can contain additional groups like hydroxyl, carboxyl or amino groups as they are typically a monoazo structure. The metal complex dye can form strong co-ordination complexes with transition metals like Chromium, Copper, Nickel, and Cobalt.