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BRIDGE COATINGS INSPECTOR PROGRAM
EXAM SCRIPT 2026 COMPREHENSIVE EXAM
Q&A STUDY GUIDE
◉ Frequency of Testing Recirculated Abrasives. Answer: Tested prior to the start and at the end of each day's blast cleaning operations, and at least once every four hours during normal operation. ◉ Determination of Steel Surface Contamination. Answer: Some signs to look for:
- The prepared surface may not have the typical "dry" appearance or may look slightly darker.
- The surface may look like it is covered with small, dark spots other than embedded abrasive.
- Airborne dust may stick to the surface and be more difficult to remove with compressed air. ◉ Removing Oil Contamination from Steel. Answer: Solvent wiping is NOT effective at removing contamination from blast cleaned steel surfaces. Other methods of solvent cleaning that are more effective, such as vapor degreasing or solvent washing followed by a clean solvent rinse, should be used whenever possible. Except for small parts that have been solvent washed and rinsed in clean solvent, all surfaces should be reblasted after oil contamination has been removed by one of the above methods.
◉ Source of Oil Contamination. Answer: Oil is often added to steel shot and grit at the mill as a rust preventative. The oil should be removed before the abrasive is used for blast cleaning. This can be done by mixing the abrasive with diatomaceous earth, which absorbs the oil, and then cycling the abrasive through a cyclone separator to remove the diatomaceous earth. The abrasive should be tested to verify that the oil was removed. Other sources are cutting oils and other lubricants that get on the surface of steel during fabrication. Since hey may contaminate recirculated abrasives, they should be removed by solvent cleaning prior to blast cleaning. ◉ Effects of Oil Contamination. Answer: Since oil is a release agent, it may interfere with the satisfactory adhesion of the applied coating or lining to the surface and result in an adhesion failure. A coating applied over an oil-contaminated surface usually has the appearance of "fish eyes" in the finish. ◉ Accept Criteria for Recirculated Abrasives. Answer: Clouding or discoloration of the water, but no oil film or slick on the surface of the water tested in accordance with this procedure.
◉ When Compressed Air Test Not Required. Answer: Not necessary if compressed air will not come in direct contact with the surface, abrasives used for surface prepartion, or coating or lining materials. Ex: air used for operation of air driven motors on units for airless spray painting. ◉ Power Tool Cleaning. Answer: If power tool cleaning is the final step in surface preparation, dry, oil-free air must be used to operate air-driven power tools. Power tool cleaning must be followed by complete solvent cleaning or chemical cleaning if oil is added to the compressed air supply for the purpose of lubricating air-driven power tools. ◉ Oil Free Compressors. Answer: Testing still required because they are still prove to moisture. ◉ Source of Oil Contamination. Answer: Almost always the equipment, usually caused by worn poston rings. Also could be due to excessive residual oil in lines caused by malfunctioning oil and moisture traps. Clogged filters should be replaced and traps should be coninuously bled so they cannot fill up and overflow back into the line. Last resort, the compressor requires an overhaul. ◉ Source of Water Contamination. Answer: Air entering the compressor contains varying amounts of water vapor, depending on the prevailing ambient temperature and relative humidity. The saturation point drops as air is compressed, making the air "wetter."
Check moisture traps, intercooler, and aftercooler. Ensure cooling water is turned on and that drains are not clogged. Last resort, consider intalling larger or additional moisture traps. ◉ Compressed Air Accept Criteria. Answer: No evidence of contamination, oil or moisture when blotter or test material is examined visually and by touch. No characteristic oil odor. ◉ Corrosion. Answer: A process whereby materials deteriorate as the result of a reaction between them and their surrounding environment. ◉ Cause of Corrosion of Iron and Steel. Answer: These metals are chemically unstable as manufactured products, and they stabilize by oxidizing and changing back to their natural iron ore forms in which they were mined. In the process of being converted into iron or steel, the iron ore acquires large amounts of energy. Its natural tendency is to stabilize and release the acquired energy (corrodes, forming rust). ◉ Components Required for Corrosion. Answer: 1. Oxygen
- Water
- A source of ions. The higher the concentration of these three, the more rapid the corrosion reaction will be.
- Epoxy coal tar
- Epoxy ester
- Epoxy phenolic
- Inorganic and organic zincs
- Silicones
- Urethanes
- Vinyls ◉ Major Components of Coatings. Answer: 1. Vehicle: Solvent and Resin (Binder)
- Pigment: Coloring Pigments and Reinforcing Pigments (Inerts) ◉ Vehicle. Answer: Consist of resin dissolved in solvent. Binds the pigments together and is the basic film-forming portion of the coating. ◉ Pigment. Answer: Contains pigments that impart color and may include extenders and reinforcing agents such as silica flour, flake glass, mica, inerts, thixotropizing agents, UV screening pigments, corrosion inhibitors, and other additives necessary to yield specific properties to the coating or lining. ◉ Mineral Spirits. Answer: Thinner used for oils and alkyds.
◉ Aromatics (benzene, xylol, toluol). Answer: Thinner used for coal tar epoxies, alkyds, and chlorinated rubbers. ◉ Ketones (MEK, MIBK). Answer: Thinner used for vinyls, epoxies, and urethanes. ◉ Alcohols (isopropyl). Answer: Thinner used for phenolics and inorganic zincs. ◉ Water. Answer: Thinner used for acrylics and some inorganic zincs. ◉ Air Oxidation. Answer: AKA air drying. Curing method for alkyds and epoxy ester. Oxygen penetrates the film after the solvent has evaporated. There is a limit to the film thickness which can be achieved. ◉ Solvent Evaporation. Answer: Curing method for vinyls, chlorinated rubber, bituminous (coal tar solutions), and acrylics. Almost all coatings, unless they are 100% solids, will undergo solvent evaporation prior to curing. The solvent completely
Thinner: Water ◉ Alkyds. Answer: Usually natural oils which have been chemically modified to improve the rate of cure, chemical resistance, and hardness. +General purpose coatings designed for application to a wide range of substrates. +Easily applied and can be used for primers or topcoats +Good color retention and gloss
- Poor chemical resistance
- Subject to saponification, which is the chemical interaction of fat with an alkali that forms a soap.
- Not suitable for application to alkaline surfaces Cure: Air Oxidation Thinner: Aromatics (benzene, xylol, toluol) ◉ Bituminous. Answer: +Low cost +Heavy bodies +Applied either hot or as a cut back with solvent +Good moisture barrier +Good to fair resistance to chemical fumes and spillage
+Good acid resistance
- Poor solvent resistance
- No corrosion inhibiting qualities
- When damaged, undercutting can be a serious problem
- Available in black only, Cure: Solvent Evaporation ◉ Chlorinated Rubber. Answer: Similar to vinyl +Fiarly tough, thin films with good abrasion resistance +Excellent weathering properties +Excellent resistance to most mineral acids and alkalies, salt and fresh water, and fungus growth Frequently modified with alkyd resins to lower their cost and improve their application characteristics. Curing: Solvent Evaporation ◉ Epoxy Amine. Answer: Catalyzed or hardened by an amine curing agent +Hard, abrasion resistant coatings with good-to-excellent alkali, acid, and solvent resistance.
- Normally black in color. Thinner: Aromatics (benzene, xylol, toluol) ◉ Epoxy Phenolic. Answer: Combine portion of phenolic resin with epoxy resin. +Usually employed as tank linings +Used extensively in nuclear plants as interior coatings for containment vessels +Good resistance to effects of radiation Thinner: Ketones (MEK, MIBK) ◉ Epoxy Ester. Answer: Combination of epoxy resin and a drying oil. +Do not require a catalyst or hardener
- Chemical resistance better than alkyds, but still rather poor +Can be applied by relatively inexperienced painters on surfaces having only marginal surface preparation
- Do not lift most old, sound paints
- Weaher resistance is fairly good, but will chalk and yellow after extended exposure to the sun +Do not saponify over alkaline surfaces to same degree as alkyd
Cure: Solvent Evaporation and Oxiation Thinner: Ketones (MEK, MIBK) ◉ Inorganic and Organic Zincs. Answer: Metallic zinc is used as the pigmentation with a variety of vehicles for inorganic and organic zinc coatings. They may be one-, two-, or three-package materials, post-cured, moisture cured, solvent based, or water based. The end product in all cases is metallic zinc suspended in an extremely hard, tough, silicate matrix.
- Acid or alkali resistance is poor +Solvent, moisture, and salt resistance is excellent +Weather extremely well +Often used as single-coat system for structural steel or tanks
- Abrasive blasting is required
- Dry film thickness of the applied film is critical Curing: Chemical Reaction (Hydrolysis) for Inorganic Zincs Thinner: Alcohols (isopropyl) and Water for inorganic zincs ◉ Silicones. Answer: Semi-inorganic polymers which, when formulated into coatings, have:
Curing: Chemical Thinner: Ketones (MBK, MIBK) ◉ Vinyls. Answer: Thermoplastic materials. +Can be applied at much lower temperatures than any catalyzed coating +Acid and alkali resistance excellent
- Poor solvent resistance +Because they are soluble in their own solvents, repairs are easily made +Outstanding weather and water resistance +Basis of Bureau of Reclamation VR-3 and VR-6 Systems (Vinyl Resin
Coats).
A clean, preferably abrasive blasted surface, is required for proper adhesion. They usually employ special primers. ◉ Dew Point. Answer: Temperature at which moisture will begin to form on a steel surface (and cause rust).
◉ Environmental Conditions to Monitor and Why. Answer: 1. Surface Temperature
- Air Temperature
- Percent Relative Humidity
- To determine if a dew point problem exists
- To help avoid potential application problems should air temperature or the substrate temperature become too hot or too cold for satisfactory film formation
- To determine the rate of cure of the applied coating or lining system ◉ Environmental Conditions Monitoring Instruments. Answer: 1. Surface Thermometer: Surface or optical pyrometer, dial thermometer with a magnetic base, direct thermocouple/thermis or other accepted field instrument.
- Wet and Dry Bulb Temperatures: Sling or battery operated psychrometer.
- Dew Point Reading: Psychrometric tables, graphs, or slide rule for determining relative humidity and dew point from wet and dry bulb temperature readings.
- Continuous recording instruments, such as thermographs, hygrograps and thermo-hygrographs may be used in conjunction with the above instruments to monitor air temperature and relative humidity.
relative humidity will be specified. During dry weather inorganic zinc primers can be sprayed with a fine water mist afte rthe solvent has evaporated from the film. ◉ Testing for Proper Curing. Answer: Film Hardness. The film is not fully cured if the coating remains soft or powdery by the end of the curing cycle. ◉ Coin Test. Answer: Often used to determine the cure of an inorganic zinc coating. Cure is checked by scraping the surface with the knurled edge of a coin. If more than only a very slight powdering occurs, proper cure has not been obtained. ◉ Other Factors to Consider. Answer: 1. Ventilation. Concern is combustible gas. If in confined space, a combustion gas alarm set at 20% of lower explosive limit wil assure adequate ventilation. Also concerned with visibility during abrasive work.
- Airborne Dust. Concern is detrimental effect on performance and appearance of the coating. ◉ Ambient Condition Accept Criteria for Abrasive Blast Cleaning. Answer: Surface temperature at least 5F above the dew point.
◉ Ambient Condition Accept Criteria for Application of Coatings or Linings. Answer: 1. Air and surface temperature within specified limits
- Surface temperature at least 5F above dew point
- Relative humidity within specified limits ◉ Why DFT Measurements Are Important. Answer: Assure that the coating or lining material was applied at the specified thickness. Improper thickness may cause early coating or lining failure. ◉ Instruments Needed to Measure DFT. Answer: 1. Dry Film Thickness Gage
- Calibration Standards
- Calibration Tools ◉ Types of DFT Instruments. Answer: 1. Magnetic Pull-off Gage
- Fixed Probe Type
- Eddy Current
- Destructive Type ◉ Magnetic Pull-Off Gage. Answer: Also referred to as a "boomerang," "dog leg," or "banana" gage because of its basic shape. Most commonly used DFT gage. The instrument balances the probe's magnetic attraction to the ferrous substrate against variable spring
