Low Temperature Formation of Inorganic Conversion Coatings for Ferrous Substrates

Invention Summary:

Coatings that provide a passivating barrier of very low solubility through a conversion of the metal surface into a corrosion-resistant, non reactive form, play an important role in coating technology. Conversion coatings are often absorbent, providing an ideal base for protective oils, waxes or dyes. They are also used for high-temperature applications and provide properties such as hardness, abrasion resistance, and adhesion and thermal stability. Chromate and phosphate conversion coatings have poor abrasion resistance and thermal stability, and preparation process requires the use of toxic chemicals and polluting ions deleterious to the environment. In comparison, oxide coatings have much better properties. However, the current state of the art uses a high temperature process that results in magnetite that does not protect against corrosion.

Rutgers University has developed a low temperature manufacturing method to form passivation coatings on ferrous substrates. The formation of these hydrated silicate coatings of acmite are ideal as a passivation layer and provide superior corrosion resistance, thermal stability and wear. The grain morphology of the passivation layer can be modified resulting in different roughness levels. Moreover, the manufacturing method does not use any chemical agents that pollute the environment.

Market Applications:

Corrosion resistant coatings have wide-spread application for iron or steel-based materials as a primer coating for paints, enamels and lacquers, to aid in cold-form- ing, impart wear resistance or color. Examples are rebar for the construction industry, brake rotors or body parts in the automotive industry or consumer products such as watch cases.


These inorganic conversion coatings provide a superior corrosion resistance, thermal stability and wear resistance, and they are applied using a low cost, green manufacturing process.

Intellectual Property & Development Status:

Two issued US patents:

  • 6,322,898, Inorganic conversion coatings for ferrous substrates, Riman and Cho, 2001
  • 6,159,552, Inorganic conversion coatings for Ferrous substrates, Riman and Cho, 2000
Rutgers ID: 1998-0015
Physical Sciences
Zolt Pukanecz
Richard Riman
Seung-Beom Cho