AMPP CP3 Technologist key terms

A system where two dissimilar conductors contact an electrolyte, producing a corrosion current. It requires an anode, cathode, electrolyte, and metallic path; removing any one element stops the corrosion reaction.

The electrode where oxidation occurs and metal dissolves, releasing electrons into the circuit. In a corrosion cell the anode is the area that loses metal and commonly shows pitting or wasting.

The electrode where reduction reactions consume electrons, such as oxygen or hydrogen reduction. The cathode does not lose metal but drives the corrosion current that makes the anode dissolve.

A conductive medium, usually a liquid or moisture film containing dissolved ions, that carries current between anode and cathode. Its conductivity and chemistry strongly affect corrosion rate and coating performance.

Formation of a thin, stable oxide film on a metal surface that slows further corrosion. Stainless steels and aluminum rely on this film, which can be damaged by chlorides or mechanical abrasion.

A ranking of metals and alloys by their corrosion potential in a specific environment such as seawater. Metals farther apart on the list form stronger galvanic couples when joined and wetted.

Accelerated attack of one metal when it is electrically coupled to a more noble metal in an electrolyte. The less noble metal becomes the anode and corrodes faster than it would alone.

A connection between two different metals that can create a galvanic couple when electrolyte bridges them. Designers isolate such joints with insulating washers or coatings to prevent accelerated attack.

Coating failure where water passes through the film and accumulates at soluble salts or contaminants on the substrate, forming blisters. Thorough surface preparation and low-permeability coatings reduce the risk.

Loss of coating adhesion around a holiday or defect caused by the alkaline environment produced at a cathodically protected surface. It is a common failure mode on buried and immersed pipelines.

The ease with which water vapor, oxygen, or ions pass through a coating film. Low permeability generally improves barrier protection, especially for immersion service.

The roughness pattern produced on a substrate by abrasive blasting or other preparation, measured as anchor profile depth. Adequate profile improves mechanical adhesion of the coating.

The microscopic peaks and valleys created on a steel surface by abrasive impact. The pattern gives the coating a mechanical key and is checked with comparators or replica tape.

Surface preparation that propels abrasive particles against a substrate to remove rust, mill scale, and old coatings while creating profile. It is the most common method for high-performance coating work.

A blast cleaning grade in which only very light staining is permitted on the prepared steel surface. It is often specified for immersion or severe-service coatings.

The most thorough blast cleaning grade, leaving a surface free of visible oil, grease, dirt, mill scale, rust, and staining. It is specified where maximum coating life is required.

Ionic contaminants such as chlorides and sulfates left on a substrate that attract moisture and promote blistering or underfilm corrosion. They are detected by conductivity or specific ion tests.

Blast cleaning that injects water into the abrasive stream to control dust and sometimes to reduce salts. It requires care to prevent flash rusting before coating application.

Rapid, light rusting of freshly blasted steel caused by moisture exposure before the coating is applied. It can impair adhesion and may require reblasting if excessive.

A thermosetting coating formed by reaction of epoxy resin with a curing agent, offering good adhesion and chemical resistance. It is widely used as a primer or intermediate coat but chalks in sunlight.

A coating based on urethane chemistry, often used as a topcoat because it resists chalking and retains gloss outdoors. It is commonly applied over epoxy intermediate coats.

A primer containing a high percentage of zinc dust that protects steel galvanically, similar to galvanizing. It is typically applied over blasted steel and topcoated for barrier protection.

A coating that protects by blocking water, oxygen, and ions from reaching the substrate rather than by electrochemical action. Performance depends heavily on film thickness and low permeability.

Exposure of a coated surface to continuous or intermittent contact with a liquid, such as tank interiors or pipelines. It demands low-permeability coatings and thorough surface preparation.

The working time after mixing a two-component coating during which it remains usable. Exceeding pot life causes viscosity rise and poor film formation, so batches must be mixed and used promptly.

A coating application method that pressurizes paint and forces it through a small orifice to atomize it without compressed air. It handles high-viscosity materials and gives high transfer efficiency.

The percentage of sprayed coating that actually lands on and adheres to the target surface. It affects material cost, overspray, and environmental release.

A discontinuity or void in a coating film that exposes the substrate, such as a pinhole or thin spot. Holidays are located with high-voltage or low-voltage detectors and then repaired.

A high-voltage inspection method that detects holidays in a coating by producing a visible spark where the film is discontinuous. It is used on conductive substrates and thicker films.

The thickness of the cured coating film, measured with magnetic or ultrasonic gauges. It is compared against specification limits and usually averaged across several readings.

The thickness of the coating immediately after application, measured with a comb or wheel gauge. Checking it during work helps control the final dry film thickness.

A test in which a dolly is bonded to the coating and pulled until failure, measuring bond strength. The failure mode (cohesive or adhesive) is recorded along with the load.

The bond between a coating and the substrate or between coats. It depends on surface cleanliness, profile, and application conditions and is verified by tests such as pull-off or cross-cut.

A project document listing the inspections, tests, acceptance criteria, and hold points required at each stage of coating work. It coordinates the contractor, inspector, and owner.

A stage in a project where work cannot proceed until a specified inspection is completed and approved. Hold points are defined in the inspection and test plan.

A written project document stating required materials, surface preparation, application, and acceptance criteria. It forms the contractual basis for inspection and dispute resolution.

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

A confined space that contains or may contain a hazardous atmosphere, engulfment, or other serious hazard, requiring a written entry permit. Coating work inside tanks and vessels often falls in this category.

Controlled movement of air into and out of a work area to remove solvent vapors, dust, and blast debris. Adequate ventilation is required for confined-space entry and spray operations.

Organic chemicals that evaporate readily from solvents and coatings and contribute to air pollution. Regulations often cap their content in coatings and require recordkeeping.

Corrosion that spreads laterally beneath a coating from a defect, often driven by chloride contamination or poor adhesion. It lifts the film and is a common cause of coating failure.

Surface degradation in which a coating binder breaks down and leaves a powdery layer. It is common with epoxies exposed to sunlight and is assessed by rubbing or tape methods.

A technique that makes a metal the cathode of a corrosion cell by supplying current from a sacrificial anode or impressed-current system. It is often combined with coatings on buried or immersed structures.