Phosphate bonded aluminum coatings

A heat curable overlay topcoat composition comprising:

• (a) phosphate ions and permanganate ions;
• (b) at least one species of metal cation having a valence greater than +1;
• (c) water;
• and
• (d) an additive selected from the group consisting of wetting agents, film-forming agents, corrosion inhibitors, dry lubricants, chromatic pigments, and combinations thereof;
• wherein the composition has a pH in the range from about 1.5 to about 4.5 and is substantially free of chromate ions and molybdate ions, said topcoat composition having a nonvolatile content of not more than about 35% by weight.

A heat curable composition comprising metallic aluminum particles dispersed in a bonding composition comprising:

• (a) phosphate ions and permanganate ions;
• (b) at least one species of metal cation having a valence greater than +1;
• and
• (c) water;
• wherein the composition has a pH in the range from about 1.5 to about 4.5 and is substantially free of chromate ions and molybdate ions.