AMPP CCI-1 key terms

The degradation of a material, usually a metal, through chemical or electrochemical reaction with its environment. For steel, this typically means iron oxidizing and losing structural integrity over time.

A system in which an anode, a cathode, an electrolyte, and a metallic path allow electron flow, driving corrosion. All four elements must be present for this type of corrosion to proceed.

The electrode where metal oxidation occurs and electrons are released. In a corrosion cell, the anode is the area that loses material, forming metal ions that enter the electrolyte.

The electrode where reduction reactions consume electrons during corrosion. The cathode does not lose metal; it supports reactions such as oxygen reduction or hydrogen evolution.

A conductive medium, usually a liquid or moisture film containing dissolved ions, that allows ionic current to flow between an anode and a cathode in a corrosion cell.

Accelerated corrosion caused when two dissimilar metals are electrically connected in an electrolyte. The more active metal becomes the anode and corrodes faster than it would alone.

A ranking of metals and alloys by their corrosion potential in a specific environment such as seawater. Metals farther apart on the list create a stronger galvanic couple when connected.

A metal with low chemical reactivity and a positive corrosion potential, such as gold or platinum. In a galvanic couple, a noble metal tends to act as the cathode and is protected.

The formation of a thin, stable oxide film on a metal surface that reduces further corrosion. Stainless steel and aluminum rely on this protective layer for corrosion resistance.

A coating that protects a substrate primarily by blocking moisture, oxygen, and ions from reaching the surface. Its effectiveness depends on film integrity and low permeability.

A pigment added to a coating that slows corrosion at the metal surface through chemical action, often by passivating the substrate or buffering local chemistry. Zinc phosphate is a common example.

A method of corrosion control in which the metal to be protected is made the cathode of a corrosion cell, either by a sacrificial anode or by an impressed direct current.

A small discontinuity, pinhole, or thin spot in a coating film that exposes the substrate or allows electrical contact through the film. Holidays are located with high-voltage or low-voltage testers.

The surface to which a coating is applied, such as steel, concrete, or aluminum. Coating performance depends heavily on the substrate's condition and preparation.

The process of cleaning and roughening a substrate before coating to remove contaminants and create a suitable surface. It is often the single largest factor in coating performance.

The microscopic roughness pattern created on a substrate by abrasive blasting or other methods. It provides mechanical keying for the coating and is measured in mils or micrometers.

A surface preparation method that propels abrasive particles at high velocity to clean and roughen a substrate. It removes mill scale, rust, and old coatings and creates anchor profile.

The particulate material used in blast cleaning, such as garnet, coal slag, or steel grit. Its size, shape, hardness, and cleanliness affect profile and contamination risk.

A published specification or visual reference defining acceptable cleanliness levels after blast cleaning, such as near-white or white metal. It lets an inspector judge surface condition objectively.

A hard oxide layer formed on steel during hot rolling. It is brittle, can flake, and must be removed before coating because it interferes with adhesion and can promote undercutting corrosion.

An unwanted substance on a surface, such as oil, grease, salt, dust, or rust, that interferes with coating adhesion or cure. Contaminants must be removed during surface preparation.

A field or laboratory method that measures soluble salts on a prepared surface, often using conductivity or test kits. Excess salts can cause blistering and premature coating failure.

The temperature at which moisture in the air begins to condense on a surface. Coating application is generally prohibited when the substrate is at or near dew point.

The amount of water vapor in the air expressed as a percentage of the maximum it can hold at a given temperature. It affects drying, curing, and condensation risk during coating work.

The temperature of the substrate being coated, measured directly rather than assumed from air temperature. It influences adhesion, cure, and condensation and is compared with dew point.

The thickness of a coating film measured immediately after application while still wet. It is used to estimate and control the final dry film thickness.

The thickness of the cured coating film, usually measured with a magnetic or eddy-current gauge. It is the primary acceptance measurement against a specification.

The percentage of a coating's volume that remains as dry film after the solvents evaporate. It relates wet film thickness to dry film thickness and affects coverage and VOC.

Volatile organic compounds, the solvent portion of a coating that evaporates during drying. Regulations limit VOC content, and it affects safety, coverage, and environmental impact.

The chemical or physical process by which a coating hardens and develops its final properties. Cure may involve solvent evaporation, oxidation, or reaction of two components.

The usable working time after mixing a multi-component coating before it becomes too viscous or begins to gel. Exceeding pot life can ruin application quality and adhesion.

The time period after application during which the next coat may be applied without surface preparation or risk of poor adhesion. Missing the window often requires abrading the surface.

Coating failure in which water passes through the film and accumulates at soluble material on the substrate, forming blisters. Soluble salts and poor adhesion increase the risk.

A tiny hole through a coating film, often caused by solvent escape, trapped air, or application defects. Pinholes can expose the substrate and start localized corrosion.

A high-voltage inspection method that detects holidays and thin spots in a coating by observing a spark or current leakage. It is used on conductive substrates and thicker films.

A reference such as a photograph, comparator, or prepared panel used to judge surface cleanliness, profile, or coating appearance consistently. It supports objective acceptance decisions.

A reference device or disc with known roughness patterns used to estimate anchor profile by touch or visual comparison. It helps confirm that blasting achieved the specified roughness.

A document that provides hazard, handling, storage, and first-aid information for a chemical product such as a coating. It is a key reference for jobsite safety planning.

An enclosed area with limited entry and exit that is not designed for continuous occupancy, such as a tank interior. Coating work there requires atmospheric testing and permits.