00450002

Monograph

A large percentage (88%) of state Departments of Transportation have changed their paint specifications since 1969; primarily for increased durability, conformance to new health and environmental regulations, and faster drying. The use of zinc-rich primers and vinyl paints has increased greatly. Surface preparation is considered the most critical factor for achieving durability. Health and environmental concerns are expected to continue to have a major impact on highway steel maintenance practices. The principal factors are limitation of the amount of volatile organic compounds (VOC) released during painting and restriction of the use of lead and chromate inhibitive pigments. While there are concerns about worker safety during sandblasting, these generally can be overcome by providing individual worker protection or by using an alternate surface preparation method. The final regulations limiting VOC emissions have not been defined. A local restriction for California of 250 grams per liter of coating is scheduled for 1982 and is planned to go to zero by 1984. Similar restrictions can be expected in other areas and will greatly limit the types of coatings that can be used. Only high solids and waterborne systems can be expected to meet this type of restriction. While such coatings are being developed, none have been tested sufficiently to warrant a recommendation for general use. Paints containing lead and chromate pigments present difficult environmental problems during blast cleaning. Laboratory and field testing of lead/chromate- free pigments indicate that these pigments do provide protection of steel, and some specific formulations perform a well as the lead and chromate materials. In general, the borate and phosphate pigments have performed better than the silicate and molybdate materials. Zinc dust, a sacrificial pigment, is recommended for lead/chromate-free protection of steel, although careful surface preparation is required for this type of primer. Satisfactory performance in a field trial is a basic requirement before a new coating system is put into general use. A nationally coordinated field study is recommended to provide evaluation of new, environmentally acceptable paint systems under actual field conditions. is recommended to provide evaluation of new, environmentally acceptable paint systems under actual field conditions.

NCHRP-4-14

v.p.

1983

Appendices (3) ; Figures; Tables

Chromates; Coatings; Corrosion protection; Durability; Environmental impacts; Field tests; Laboratory tests; Lead compounds; Molybdenum; Organic compounds; Phosphates; Pollutants; Regulations; Silicates; Specifications; Structural steel; Surface preparation; Zinc rich paint

Environment; Geotechnology; Highways; Law; Materials; I35: Miscellaneous Materials

TRIS, TRB

Aug 27 2004 9:52PM