AMPP Bridge Coatings key terms

Abrasive blast cleaning that removes nearly all mill scale, rust, and old coating, leaving no more than very light staining on about five percent of the surface.

The most thorough blast cleaning grade; it removes all visible mill scale, rust, paint, and foreign matter, leaving a uniform gray-white surface with a roughened profile.

Abrasive blast cleaning that removes all visible oil, grease, dirt, mill scale, rust, and coating, while permitting staining on up to one-third of the surface.

The small-scale roughness produced on steel by blasting or power tooling; it provides a mechanical key for the coating and is measured in mils or micrometres.

A hard oxide layer formed on hot-rolled steel during production; it is brittle, can flake off, and must be removed before coating to prevent premature failure.

Chlorides, sulfates, and other water-soluble contaminants on a surface; they pull moisture through coatings and cause blistering and corrosion, so they are tested before painting.

Preparation using power-driven wire brushes, grinders, or sanders to remove loose rust, mill scale, and coating; it leaves a shallower profile than abrasive blasting.

Preparation using high-pressure water to remove contaminants, loose coating, and rust without abrasive; the cleaned surface is graded by flash-rust level from WJ-1 to WJ-4.

A primer with a high concentration of zinc dust that protects steel galvanically; the zinc corrodes sacrificially, shielding the underlying metal, and is common as the first coat on bridges.

A thermosetting resin coating used as a build coat in a multi-coat system; it provides barrier protection, adhesion, and a suitable base for the topcoat.

A topcoat based on aliphatic polyurethane resin that resists sunlight, chalking, and yellowing; it gives exterior bridges durable color and gloss.

The percentage of a coating's volume that remains as dry film after solvents evaporate; higher volume solids usually mean fewer coats and lower solvent emissions.

Organic solvents and other volatile substances that evaporate from a coating during application and cure; they are regulated because they help form air pollution and ozone.

The usable time after mixing a two-component coating during which it can still be applied properly; exceeding it causes thickening, poor flow, and weak cure.

The waiting period after mixing a two-component coating, before application, that lets the components react and the mixture become workable.

A coating that protects steel mainly by blocking water, oxygen, and ions from reaching the surface, rather than by galvanic action or corrosion inhibitors.

A project document defining surface preparation, primer, intermediate, and topcoat products, dry film thicknesses, and application requirements for the bridge coating work.

The temperature at which air becomes saturated and water vapor condenses; painting must stop when the steel temperature is at or near the dew point.

The amount of water vapor in the air shown as a percentage of saturation; high values slow solvent evaporation and cure and can cause coating defects.

The time after a coat dries during which the next coat may be applied without surface treatment; missing it can require abrading the surface to restore adhesion.

A method that forces coating through a small orifice at high pressure, atomizing it without compressed air; it gives high production on large bridge areas.

Fine coating droplets that miss the target and settle on nearby surfaces; they can cause roughness or contamination and are controlled by containment and proper spraying technique.

A separate coat brushed into welds, edges, corners, bolts, and other hard-to-spray areas before the full coat, ensuring adequate thickness where spray cannot reach.

The thickness of the cured coating measured on the steel; it is checked with magnetic or eddy-current gauges and compared with the specification limits.

The thickness of a coating just after application, measured with a comb gauge; it is used with volume solids to estimate the final dry film thickness.

A test that finds pinholes, voids, or thin spots in a coating using a low- or high-voltage electrical detector; common on immersed or lined surfaces.

A test in which a dolly is glued to the coating and pulled off to measure the force needed to detach it and to identify the failure mode.

A field test for soluble salts in which a patch is sealed to the surface, distilled water is injected and removed, and the extract is analyzed.

A foam tape pressed onto a blasted surface that captures the profile; measuring its compressed thickness with a micrometer gives the surface roughness.

Checking and adjusting an instrument against a known reference so its readings are accurate; thickness, profile, and salt-test instruments need regular calibration.

A document listing a product's hazards, ingredients, safe handling, personal protection, first aid, and spill response; it must be available where coating materials are used.

A work area with limited entry and exit that is not meant for continuous occupancy; coating work in bridge boxes or voids may need permits, ventilation, and rescue plans.

A mineral present in sand, concrete, and some blasting abrasives; breathing its dust can cause silicosis, so dust controls and respiratory protection are required.

Temporary structures and covers that enclose blasting and painting areas to capture dust, overspray, and debris and keep them from escaping.

Paint containing lead pigments or driers, often found on older bridges; removing it requires special containment, worker protection, and regulated waste handling.

A documented review of each task that identifies hazards and the controls to use before work starts; it supports safe planning for blasting, painting, and inspection.

Product data, certificates, and samples sent to the owner or engineer for approval before coating work begins, showing that materials meet the specification.