CHEMICALLY INDUCED DEGRADATION: PART 3, PIGMENTS

This third of three articles on chemically induced degradation of coatings examines chemical attack on pigments. Pigments are the second largest volumetric component of the paint film, after the binder volume. Therefore, chemical sensitivity of pigments is critical. The process of pigmentation introduces a discontinuous phase along with intrafilm interfaces. Even at low ratios of pigment volume concentration to critical pigment volume concentration, where excessive porosity is not a factor, pigmentation may decrease chemical resistance. A specific pigment, however, may itself be quite resistant to the chemical species. Flat, platy pigments will increase the film's resistance to penetrants. Although many inorganic pigments offer excellent resistance to chemicals, certain inorganics may be vulnerable to either acid or alkaline attack, and sometimes both. This attack will not only disrupt the film but also may cause additional problems because of the residues of the reaction after the attack. The "frosting" of exterior latex paints is a result of chemical effects. This defect is directly related to the attack of acids on reactive pigmentations, particularly those involving calcium carbonate. Many of the organic pigments have surprisingly good acid and alkali resistance, especially to dilute reagents. Unlike the inorganics, many organics are also prone to attack and slight dissolution in a range of organic solvents. By their very nature, corrosion-inhibitive pigments are reactive species and will serve as sites for attack by external reagents.

  • Availability:
  • Supplemental Notes:
    • Page Range: pp 58-61, 63-64
  • Corporate Authors:

    Technology Publishing Company

    2100 Wharton Street, Suite 310
    Pittsburgh, PA  United States  15203
  • Authors:
    • Hare, C H
  • Publication Date: 2000-2

Language

  • English

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: 6 p.
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00789018
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Mar 26 2000 12:00AM