AMPP CP3 Technologist cheat sheet

A coating protects by forming a continuous barrier, by barrier plus inhibitive pigments, or by galvanic (sacrificial) action; each mechanism fails differently and is inspected differently.

Corrosion is an electrochemical cell requiring anode, cathode, electrolyte, and metallic path; removing any one element stops the cell, which is why dry, clean, continuous films work.

Anodic reaction: M -> M(n+) + ne-; cathodic reaction in neutral aerated water: O2 + 2H2O + 4e- -> 4OH-; in acid: 2H+ + 2e- -> H2.

Faraday's law: mass loss = (I x t x M)/(n x F), with F = 96,485 C/mol; doubling current density doubles metal loss for a given exposure time.

Galvanic series ranking in seawater (active to noble): magnesium, zinc, aluminum, cadmium, steel, lead, tin, copper, brass, bronze, stainless (passive), titanium, graphite.

Anode-to-cathode area ratio governs severity: a small anode coupled to a large cathode concentrates current density and produces rapid localized penetration.

Osmotic blistering occurs when soluble salts or hydrophilic material under the film draw water through the coating; surface salt removal is the controlling prevention measure.

Coating adhesion is mechanical interlock, chemical bonding, and sometimes polar interaction; water displacement at the interface (cathodic disbondment) degrades all three.

Permeability, dry film thickness, and pigment volume concentration (PVC) interact: above critical PVC (CPVC), voids form and barrier protection collapses.

NACE/SSPC joint abrasive blast standards: No. 1 / SSPC-SP 5 white metal; No. 2 / SP 10 near-white; No. 3 / SP 6 commercial; No. 4 / SP 7 brush-off; No. 8 / SP 2 hand tool; No. 9 / SP 3 power tool.

SSPC-SP 10 (near-white) permits staining on no more than 5% of each unit area of surface; SSPC-SP 6 (commercial) permits staining on no more than 33%.

ISO 8501-1 visual grades: Sa 3 (blast to visually clean), Sa 2 1/2 (very thorough), Sa 2 (thorough), Sa 1 (light); St 3, St 2 for hand and power tool cleaning.

ISO 8501-1 rust grades A (intact mill scale) through D (general pitting); grade D requires more aggressive preparation and often a higher surface profile.

Abrasive profile is specified per ISO 8503-1/-2 or SSPC-VIS 1 comparators; typical epoxy and zinc-rich specifications call for 50-75 micrometres (2-3 mil) profile.

Angular, hard abrasives (aluminum oxide, steel grit) cut a sharper profile than rounded ones (sand, glass bead); profile shape affects adhesion more than amplitude alone.

Soluble salt limits are commonly tested per ISO 8502-6/-9 (Bresle) with conductivity measured per ISO 8502-9; chloride limits of 20-50 mg/m2 are typical for immersion service.

Ambient conditions per ISO 8502-4: substrate temperature must be at least 3 degrees C above dew point, and relative humidity is normally capped at 85% for blast and application.

Waterjetting standards: NACE No. 5 / SSPC-SP 12 defines WJ-1 (clean to base metal), WJ-2 (very thorough), WJ-3 (thorough), WJ-4 (light); flash rust grades are assessed per NACE VIS 7 / SSPC-VIS 4.

Generic families: alkyds (single-pack, poor alkali resistance), acrylics (fast dry, limited solvent/immersion resistance), epoxies (excellent adhesion and chemical resistance, chalk in UV), polyurethanes (UV-stable topcoats), zinc-rich primers (galvanic), fluoropolymers (high-temperature and chemical).

Epoxy chemistry cures by amine or amide addition; low-temperature grades use modified amines, and amine blush (carbamate) can form at low temperature or high humidity and must be removed before recoating.

Zinc-rich primers protect galvanically when zinc dust exceeds roughly 80% by weight in the dry film and the zinc particles contact each other and the steel.

Polyurethane topcoats are commonly aliphatic for color and gloss retention; aromatic polyurethanes yellow in UV and are used for interior or non-exposed service.

Coal tar epoxy is largely restricted by regulatory and worker-exposure concerns; modified and phenolic epoxies frequently substitute in immersion and tank lining work.

Immersion linings are selected by chemical concentration and temperature; manufacturers publish chemical resistance charts that must be consulted at the actual service temperature, not ambient.

Cathodic disbondment resistance is critical for coatings on cathodically protected buried or submerged steel; test per ISO 15711 or CSA Z245.20-02 methods.

High-temperature service requires silicone, silicone-hybrid, or fluoropolymer systems; conventional epoxies degrade above roughly 120 degrees C continuous service.

Airless spray pressure is typically 10-25 MPa (1,500-3,600 psi) with tip sizes from about 0.011 to 0.021 inch; orifice size and fan width control film build and overspray.

Tip wear enlarges the orifice and lowers pressure, reducing atomization quality; tips are replaced when flow increases measurably or the fan pattern degrades.

Conventional air spray uses lower viscosity material and produces more overspray and bounce-back; it is inefficient for high-build coatings.

Stripe coating applies extra material to edges, welds, cutouts, and fasteners before full-coat application to compensate for thin films over sharp geometry.

Wet film thickness (WFT) is measured with a comb gauge; DFT = WFT x percent volume solids of the mixed product.

Pot life is the usable time after mixing; exceeding it causes viscosity rise, poor flow, and incomplete cure. Induction time is the interval between mixing and use for some products.

Plural-component (2K) equipment meters and mixes base and curing agent at a fixed ratio; ratio verification and solvent flush procedures are required at start-up and shutdown.

Recoating intervals are set by the manufacturer: too soon causes solvent entrapment and wrinkling; too late requires surface abrasion to restore adhesion.

Each gauge reading must be a mean of three spot measurements; SSPC-PA 2 defines a spot as the average of three readings and a test area of 100 square feet (approximately 9.3 square metres).

SSPC-PA 2 Type 1 gauges are magnetic pull-off; Type 2 are constant-pressure magnetic; Type 3 are eddy current; Type 4 are ultrasonic; Type 5 are pendulum.

SSPC-PA 2 acceptance: for DFT up to 30 mils, each spot must be at least 80% of specified minimum and no spot may exceed 120% of specified maximum; the average must fall within the specified range.

Holiday (spark) testing uses wet-sponge low voltage for thin films and high-voltage DC for thick films; voltage is set from film thickness and dielectric strength, and excess voltage can damage sound film.

Adhesion tests: ASTM D3359 tape (cross-cut, classes 5B to 0B) for films under about 5 mils; ASTM D4541 pull-off for thicker films, reported in MPa or psi with the failure mode.

Pull-off adhesion failure modes are expressed as percentages of adhesive (between coats or at substrate) versus cohesive (within a layer) failure.

Surface profile is measured per ASTM D4417: Method B uses a depth micrometer with replica tape, Method C uses a stylus instrument; results are reported in micrometres or mils.

Environmental monitoring records air temperature, substrate temperature, dew point, and relative humidity at the start, during, and at the end of each shift.

A coating specification states scope, surface preparation standard, products and manufacturers, DFT per coat, stripe coat requirements, environmental limits, inspection hold points, and acceptance criteria.

Order of precedence in a contract typically places the contract, then drawings, then the technical specification, then referenced standards; conflicts must be resolved in writing before work begins.

SSPC-PA 1 covers shop, field, and maintenance painting practices; SSPC-PA 2 covers measurement of DFT; SSPC-Guide 6 addresses overcoating.

Inspection and Test Plans (ITPs) list hold points, witness points, and review points; work may not proceed past a hold point without documented sign-off.

Material certificates, batch numbers, and shelf-life data are retained in the quality record to allow traceability if a failure occurs later.

Nonconformance reports document the deviation, disposition, and corrective action; rework is tracked to closure before final acceptance.

As-built documentation includes final DFT maps, environmental logs, holiday test results, adhesion results, and product data sheets of the products actually applied.

Abrasive blasting requires supplied-air respiratory protection (Type CE abrasive-blasting respirator) and hearing protection; silica sand is prohibited or severely restricted in many jurisdictions due to silicosis risk.

Confined-space entry requires atmospheric testing for oxygen (19.5-23.5%), flammables, and toxics, plus an attendant, entry permit, and rescue plan.

Solvent-based coatings raise fire and explosion risk; equipment must be bonded and grounded, and ventilation must keep concentrations below the lower explosive limit.

VOC content is regulated by regional rules; compliant coatings are often high-solids or waterborne, and thinning can push a compliant product out of compliance.

Lead and chromate pigments trigger specific worker-protection and waste-disposal obligations; removal debris may be a regulated hazardous waste requiring characterization and manifesting.

Spent abrasive and coating debris are characterized (for example by TCLP) before disposal; disposal options depend on the analytical results.

Safety Data Sheets (SDS) under the GHS format supply hazard, PPE, and first-aid information; they must be available at the point of use.

Failure investigation sequence: document the site and conditions, record the coating system and history, sample the failed and sound areas, perform laboratory analysis, then determine root cause before specifying repair.

Common failure signatures: blistering (osmosis or solvent entrapment), blistering with rust (salt contamination), checking and cracking (excess DFT or UV degradation), wrinkling (recoat too soon or incompatible thinner), and pinpoint rusting (thin film or inadequate cleaning).

Cathodic disbondment appears as a dished, clean-metal area around a coating defect on cathodically protected steel; it is not a coating application defect alone.

Underfilm corrosion at scribes is assessed by salt-spray or cyclic tests (ASTM B117, ISO 9227, ASTM D5894) with scribe creep measured in millimetres.

Repair boundaries must extend beyond visible damage into sound, well-bonded coating, feathered to a taper, with preparation matched to the original specification.

Chalking is surface pigment and binder degradation from UV exposure; it is assessed per ASTM D4214 and usually requires removal before recoating.

Intercoat contamination (oil, dust, amine blush) causes delamination at the interface; the failure mode in a pull-off test identifies which interface is at fault.

A coating protects by forming a continuous barrier, by barrier plus inhibitive pigments, or by galvanic (sacrificial) action; each mechanism fails differently and is inspected differently.

Corrosion is an electrochemical cell requiring anode, cathode, electrolyte, and metallic path; removing any one element stops the cell, which is why dry, clean, continuous films work.

Anodic reaction: M -> M(n+) + ne-; cathodic reaction in neutral aerated water: O2 + 2H2O + 4e- -> 4OH-; in acid: 2H+ + 2e- -> H2.

Faraday's law: mass loss = (I x t x M)/(n x F), with F = 96,485 C/mol; doubling current density doubles metal loss for a given exposure time.

Galvanic series ranking in seawater (active to noble): magnesium, zinc, aluminum, cadmium, steel, lead, tin, copper, brass, bronze, stainless (passive), titanium, graphite.

Anode-to-cathode area ratio governs severity: a small anode coupled to a large cathode concentrates current density and produces rapid localized penetration.

Osmotic blistering occurs when soluble salts or hydrophilic material under the film draw water through the coating; surface salt removal is the controlling prevention measure.

Coating adhesion is mechanical interlock, chemical bonding, and sometimes polar interaction; water displacement at the interface (cathodic disbondment) degrades all three.

Permeability, dry film thickness, and pigment volume concentration (PVC) interact: above critical PVC (CPVC), voids form and barrier protection collapses.

NACE/SSPC joint abrasive blast standards: No. 1 / SSPC-SP 5 white metal; No. 2 / SP 10 near-white; No. 3 / SP 6 commercial; No. 4 / SP 7 brush-off; No. 8 / SP 2 hand tool; No. 9 / SP 3 power tool.

SSPC-SP 10 (near-white) permits staining on no more than 5% of each unit area of surface; SSPC-SP 6 (commercial) permits staining on no more than 33%.

ISO 8501-1 visual grades: Sa 3 (blast to visually clean), Sa 2 1/2 (very thorough), Sa 2 (thorough), Sa 1 (light); St 3, St 2 for hand and power tool cleaning.

ISO 8501-1 rust grades A (intact mill scale) through D (general pitting); grade D requires more aggressive preparation and often a higher surface profile.

Abrasive profile is specified per ISO 8503-1/-2 or SSPC-VIS 1 comparators; typical epoxy and zinc-rich specifications call for 50-75 micrometres (2-3 mil) profile.

Angular, hard abrasives (aluminum oxide, steel grit) cut a sharper profile than rounded ones (sand, glass bead); profile shape affects adhesion more than amplitude alone.

Soluble salt limits are commonly tested per ISO 8502-6/-9 (Bresle) with conductivity measured per ISO 8502-9; chloride limits of 20-50 mg/m2 are typical for immersion service.

Ambient conditions per ISO 8502-4: substrate temperature must be at least 3 degrees C above dew point, and relative humidity is normally capped at 85% for blast and application.

Waterjetting standards: NACE No. 5 / SSPC-SP 12 defines WJ-1 (clean to base metal), WJ-2 (very thorough), WJ-3 (thorough), WJ-4 (light); flash rust grades are assessed per NACE VIS 7 / SSPC-VIS 4.

Generic families: alkyds (single-pack, poor alkali resistance), acrylics (fast dry, limited solvent/immersion resistance), epoxies (excellent adhesion and chemical resistance, chalk in UV), polyurethanes (UV-stable topcoats), zinc-rich primers (galvanic), fluoropolymers (high-temperature and chemical).

Epoxy chemistry cures by amine or amide addition; low-temperature grades use modified amines, and amine blush (carbamate) can form at low temperature or high humidity and must be removed before recoating.

Zinc-rich primers protect galvanically when zinc dust exceeds roughly 80% by weight in the dry film and the zinc particles contact each other and the steel.

Polyurethane topcoats are commonly aliphatic for color and gloss retention; aromatic polyurethanes yellow in UV and are used for interior or non-exposed service.

Coal tar epoxy is largely restricted by regulatory and worker-exposure concerns; modified and phenolic epoxies frequently substitute in immersion and tank lining work.

Immersion linings are selected by chemical concentration and temperature; manufacturers publish chemical resistance charts that must be consulted at the actual service temperature, not ambient.

Cathodic disbondment resistance is critical for coatings on cathodically protected buried or submerged steel; test per ISO 15711 or CSA Z245.20-02 methods.

High-temperature service requires silicone, silicone-hybrid, or fluoropolymer systems; conventional epoxies degrade above roughly 120 degrees C continuous service.

Airless spray pressure is typically 10-25 MPa (1,500-3,600 psi) with tip sizes from about 0.011 to 0.021 inch; orifice size and fan width control film build and overspray.

Tip wear enlarges the orifice and lowers pressure, reducing atomization quality; tips are replaced when flow increases measurably or the fan pattern degrades.

Conventional air spray uses lower viscosity material and produces more overspray and bounce-back; it is inefficient for high-build coatings.

Stripe coating applies extra material to edges, welds, cutouts, and fasteners before full-coat application to compensate for thin films over sharp geometry.

Wet film thickness (WFT) is measured with a comb gauge; DFT = WFT x percent volume solids of the mixed product.

Pot life is the usable time after mixing; exceeding it causes viscosity rise, poor flow, and incomplete cure. Induction time is the interval between mixing and use for some products.

Plural-component (2K) equipment meters and mixes base and curing agent at a fixed ratio; ratio verification and solvent flush procedures are required at start-up and shutdown.

Recoating intervals are set by the manufacturer: too soon causes solvent entrapment and wrinkling; too late requires surface abrasion to restore adhesion.

Each gauge reading must be a mean of three spot measurements; SSPC-PA 2 defines a spot as the average of three readings and a test area of 100 square feet (approximately 9.3 square metres).

SSPC-PA 2 Type 1 gauges are magnetic pull-off; Type 2 are constant-pressure magnetic; Type 3 are eddy current; Type 4 are ultrasonic; Type 5 are pendulum.

SSPC-PA 2 acceptance: for DFT up to 30 mils, each spot must be at least 80% of specified minimum and no spot may exceed 120% of specified maximum; the average must fall within the specified range.

Holiday (spark) testing uses wet-sponge low voltage for thin films and high-voltage DC for thick films; voltage is set from film thickness and dielectric strength, and excess voltage can damage sound film.

Adhesion tests: ASTM D3359 tape (cross-cut, classes 5B to 0B) for films under about 5 mils; ASTM D4541 pull-off for thicker films, reported in MPa or psi with the failure mode.

Pull-off adhesion failure modes are expressed as percentages of adhesive (between coats or at substrate) versus cohesive (within a layer) failure.

Surface profile is measured per ASTM D4417: Method B uses a depth micrometer with replica tape, Method C uses a stylus instrument; results are reported in micrometres or mils.

Environmental monitoring records air temperature, substrate temperature, dew point, and relative humidity at the start, during, and at the end of each shift.

A coating specification states scope, surface preparation standard, products and manufacturers, DFT per coat, stripe coat requirements, environmental limits, inspection hold points, and acceptance criteria.

Order of precedence in a contract typically places the contract, then drawings, then the technical specification, then referenced standards; conflicts must be resolved in writing before work begins.

SSPC-PA 1 covers shop, field, and maintenance painting practices; SSPC-PA 2 covers measurement of DFT; SSPC-Guide 6 addresses overcoating.

Inspection and Test Plans (ITPs) list hold points, witness points, and review points; work may not proceed past a hold point without documented sign-off.

Material certificates, batch numbers, and shelf-life data are retained in the quality record to allow traceability if a failure occurs later.

Nonconformance reports document the deviation, disposition, and corrective action; rework is tracked to closure before final acceptance.

As-built documentation includes final DFT maps, environmental logs, holiday test results, adhesion results, and product data sheets of the products actually applied.

Abrasive blasting requires supplied-air respiratory protection (Type CE abrasive-blasting respirator) and hearing protection; silica sand is prohibited or severely restricted in many jurisdictions due to silicosis risk.

Confined-space entry requires atmospheric testing for oxygen (19.5-23.5%), flammables, and toxics, plus an attendant, entry permit, and rescue plan.

Solvent-based coatings raise fire and explosion risk; equipment must be bonded and grounded, and ventilation must keep concentrations below the lower explosive limit.

VOC content is regulated by regional rules; compliant coatings are often high-solids or waterborne, and thinning can push a compliant product out of compliance.

Lead and chromate pigments trigger specific worker-protection and waste-disposal obligations; removal debris may be a regulated hazardous waste requiring characterization and manifesting.

Spent abrasive and coating debris are characterized (for example by TCLP) before disposal; disposal options depend on the analytical results.

Safety Data Sheets (SDS) under the GHS format supply hazard, PPE, and first-aid information; they must be available at the point of use.

Failure investigation sequence: document the site and conditions, record the coating system and history, sample the failed and sound areas, perform laboratory analysis, then determine root cause before specifying repair.

Common failure signatures: blistering (osmosis or solvent entrapment), blistering with rust (salt contamination), checking and cracking (excess DFT or UV degradation), wrinkling (recoat too soon or incompatible thinner), and pinpoint rusting (thin film or inadequate cleaning).

Cathodic disbondment appears as a dished, clean-metal area around a coating defect on cathodically protected steel; it is not a coating application defect alone.

Underfilm corrosion at scribes is assessed by salt-spray or cyclic tests (ASTM B117, ISO 9227, ASTM D5894) with scribe creep measured in millimetres.

Repair boundaries must extend beyond visible damage into sound, well-bonded coating, feathered to a taper, with preparation matched to the original specification.

Chalking is surface pigment and binder degradation from UV exposure; it is assessed per ASTM D4214 and usually requires removal before recoating.

Intercoat contamination (oil, dust, amine blush) causes delamination at the interface; the failure mode in a pull-off test identifies which interface is at fault.