The commercial application of black conversion coatings to iron, steel, and cast iron. Blackening of ferrous metals.The three most economically viable methods of blackening ferrous alloys-hot alkaline black oxiding, room temperature black oxiding, and black zinc phosphate-are chosen for a number of reasons. These are:

1. They produce an attractive black finish that enhances the saleability of the
articles thus coated.

2. They offer an economical means of imparting moderate corrosion resistance
to the articles thus coated.

3. They yield a finish that when properly sealed resists galling and enhances
lubricity.

4. Their application is economical as far as cost per square foot.

5. These finishes yield little or no dimensional change.