Identifying and Removing Corrosion for the A&P Practical

October 25, 2026 · Primary sources checked October 20, 2026

For Airframe and Powerplant (A&P) practical corrosion removal, organize your O&P (oral and practical) rehearsal around inspection, a metal-specific removal method and restored surface protection.

What does this O&P task evaluate?

For this rehearsal, connect inspection, material selection and restoration of protection to the Federal Aviation Administration (FAA) Airman Certification Standards (ACS) skills below.

A practical assignment joins one skill element to two related practical questions. Available, applicable references are permitted while completing both parts of that assignment.

Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929, printed 16, PDF 16, 5-5-11-7C3)c)

The individual project is evaluated against a pass/fail standard. The pass/fail decision for a project requires the skill to succeed on the first attempt and the two associated questions to be answered successfully.

Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929, printed 16, PDF 16, 5-5-11-7C3)f)

The downloaded test defines the performance standard for the assigned corrosion task. The Mechanic Test Generator (MTG) FAQ says the practical portion uses separate projects that cannot be combined.

Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929, printed 16, PDF 16, 5-5-11-7C3)g) · FAA Mechanic Test Generator FAQs, updated May 22, 2023, unnumbered page, PDF 4

The official sample test labels its contents as examples for practice purposes only.

FAA sample oral and practical test, unnumbered page, PDF 6

FAA-S-ACS-1, printed 12, PDF 17

Our scope is a surface-corrosion rehearsal tied to those skills, not a promise that every applicant receives a corrosion-removal project.

Control the chemical and abrasion risks first

In the ACS safety appendix, the evaluator ensures that the applicant follows all safety recommendations and precautions, including use of current maintenance and overhaul publications and procedures. The ACS includes required personal protective equipment (PPE), with safety glasses and hearing protection given as examples.

FAA-S-ACS-1, printed A-3, PDF 67

Any disregard for safety is not tolerated and will result in a failure. For a project action that would jeopardize safety, the evaluator will direct simulation of that portion.

FAA-S-ACS-1, printed A-3, PDF 67

• Consult the Safety Data Sheet (SDS) for every chemical used during corrosion-control maintenance.
• Pay particular attention to the SDS protective measures, including gloves, respirators and face shields.
• Solvents and cleaning liquids, including products considered environmentally friendly, can damage the skin, internal organs or nervous system.
• Active solvents such as methyl ethyl ketone (MEK) and acetone can be harmful or fatal if swallowed, inhaled or absorbed through the skin in sufficient quantities.
• Surface-treatment chemicals must be handled with extreme care and mixed exactly as directed.
• Some surface-treatment chemicals react violently when accidentally mixed with paint thinners.
• Chemical paint removal over a large area is to be done outdoors wherever practicable, preferably in shade; indoor work requires assured adequate ventilation.
• For toxic paint stripper, wear rubber gloves, an acid-repellent apron and goggle-type eye protection because its ingredients harm skin and eyes.
• Synthetic rubber, tires, fabric and acrylic surfaces must be thoroughly protected from paint remover.
• Exercise care near gas- or watertight seam sealants because stripper tends to soften them and destroy their integrity.
• Mask openings that could admit stripping compound into aircraft interiors or critical cavities.
• Use only nonmetallic scrapers to help remove persistent paint, and do not reuse a stripper-exposed brush for another purpose.
• Rinsing must completely remove the cleaned area’s stripper residues, and stripped waste needs disposal in accordance with environmental laws.
• Our dust-control preparation: identify the abrasive, coating and dust exposure before sanding, and select the extraction and respiratory protection specified for those materials.

FAA-H-8083-30B, General, printed 8-10, PDF 334 · FAA-H-8083-30B, General, printed 8-27, PDF 351 · FAA-H-8083-30B, General, printed 8-22, PDF 346 · FAA-H-8083-30B, General, printed 8-14, PDF 338 · FAA-H-8083-30B, General, printed 8-15, PDF 339

Inspect before deciding how much metal to remove

Start every corrosion inspection by thoroughly cleaning the inspection area. Follow with a general visual inspection, then a detailed examination of damaged or suspect locations.

FAA-H-8083-30B, General, printed 8-11, PDF 335

• Look for general roughening, etching or pitting, often accompanied by powdery corrosion products.
• Treat tiny visible pit openings seriously: they may penetrate deeply into a structural member.
• Worm-like traces beneath a paint film identify filiform corrosion.
• Lifting surface grains characterize exfoliation, an advanced form of intergranular corrosion.
• Intergranular corrosion may be present without visible surface evidence.
• Obtain adequate inspection access by removing access panels and adjacent equipment and cleaning as necessary.
• Nondestructive inspection (NDI) methods have limitations and must be performed only by qualified and certified NDI personnel.
• Eddy-current, X-ray and ultrasonic equipment needs calibration each time it is used and a controlling reference standard for reliable results.

FAA-H-8083-30B, General, printed 8-5, PDF 329 · FAA-H-8083-30B, General, printed 8-6, PDF 330 · FAA-H-8083-30B, General, printed 8-7, PDF 331 · FAA-H-8083-30B, General, printed 8-11, PDF 335

Replace a part when severe corrosion exceeds the damage limits established by its aircraft or parts manufacturer. Damage repairable by patching or insertion must be repaired under the applicable structural repair manual.

FAA-H-8083-30B, General, printed 8-14, PDF 338 · FAA-H-8083-30B, General, printed 8-20–8-21, PDF 344, 345

Choose the removal method for the metal and finish

A complete treatment cleans and strips the area, removes corrosion products as practicable, neutralizes residues, restores surface films and applies a coating or paint. Repair of corrosion damage includes removing all corrosion and its products.

FAA-H-8083-30B, General, printed 8-14, PDF 338

Aluminum, Alclad and anodized aluminum

• Do not transfer a nonwoven abrasive pad from one metal type to another.
• Steel wool, steel wire brushes and harsh abrasives are prohibited on aluminum, as is producing a buffed or wire-brush finish.
• Preserve the protective Alclad layer by avoiding unnecessary mechanical removal and exposure of its more susceptible base alloy.
• Choose a neutral-pH cleaner for the handbook’s unpainted-aluminum sequence because trapped caustic consumer cleaners can induce corrosion in lap joints.
• Clad-aluminum metal polish must not be used on anodized aluminum because it removes the protective anodized film.
• On anodized surfaces, avoid destroying the oxide film in unaffected areas and take every precaution to retain as much protective coating as practicable.
• For intergranular attack, all corrosion products and visibly delaminated layers must be mechanically removed to determine the extent of the destruction and evaluate remaining structural strength.
• Any loss of structural strength must be evaluated before repair or replacement; a designated engineering representative may assess damage not adequately addressed by manufacturer limits.
• Before blending aluminum structure, remove steel nut plates and fasteners; embedded steel or copper particles can become future corrosion sites.
• Remove all corrosion products during blending to prevent recurrence.
• Our rehearsal boundary: use the aircraft’s rework dimensions and remaining-thickness limits rather than turning handbook blend sketches into universal allowances.

FAA-H-8083-30B, General, printed 8-6, PDF 330 · FAA-H-8083-30B, General, printed 8-22, PDF 346 · FAA-H-8083-30B, General, printed 8-18, PDF 342 · FAA-H-8083-30B, General, printed 8-19, PDF 343 · FAA-H-8083-30B, General, printed 8-15, PDF 339

All corrosion-rework depressions must be faired or blended into the surrounding surface, with all corrosion and rough edges removed. Dish-outs must be elliptical, with the major axis spanwise on wings and horizontal stabilizers, lengthwise on fuselages and vertical on vertical stabilizers. In critical or highly stressed areas, remaining pits must be blended out to prevent stress risers that may cause stress-corrosion cracking. On noncritical structure, pits left after abrasive blasting need not be blended out because doing so unnecessarily removes metal. The handbook describes smoothly blended dish-outs with a 20:1 length-to-depth ratio and requires removing intervening material among closely spaced pits to minimize waviness. As an arithmetic illustration only, a depth of 0.010 inch at a 20:1 length-to-depth ratio gives a minimum length of 0.200 inch, because the handbook figure labels the length as 20 times depth minimum; the applicable aircraft limits still control the work.

FAA-H-8083-30B, General, printed 8-15, PDF 339 · FAA-H-8083-30B, General, printed 8-16, PDF 340

Steel and highly stressed steel

• All rust must be removed from steel surfaces if the corrosive attack is to be completely controlled.
• Where paint failure or mechanical damage exposes highly stressed steel, even the smallest amount of rust is potentially dangerous and must be removed and controlled; rust removal from structural components, followed by inspection and damage assessment, must be done as soon as feasible.
• Abrasive cleanup usually leaves residual rust in the bottom of small pits and crevices, making complete corrosion-product removal by abrasive or polishing methods alone practically impossible.
• For chemical rust removal, remove the steel part from the airframe if at all possible, because it can be nearly impossible to remove all residue; any caustic rust remover also requires isolating the part from nonferrous metals during treatment.
• Chemical inhibitors on installed steel parts are very dangerous because entrapped corrosive solutions can cause uncontrolled attack.
• Any corrosion on a highly stressed steel part is potentially dangerous, and its corrosion products must be removed by careful processing with mild abrasives; surface scratches or overheating-related surface changes can also cause sudden failure of these parts.
• It is essential not to overheat steel during buffing, and protective paint must be reapplied immediately after careful surface-corrosion removal.
• Chemical corrosion removers are prohibited on high-strength steel without engineering authorization because of hydrogen embrittlement.

FAA-H-8083-30B, General, printed 8-15, PDF 339 · FAA-H-8083-30B, General, printed 8-16, PDF 340 · FAA-H-8083-30B, General, printed 8-16–8-17, PDF 340, 341 · FAA-H-8083-30B, General, printed 8-17, PDF 341

Magnesium and titanium

If magnesium skin can easily be removed, do so for complete treatment; when insulating washers are involved, loosen screws enough for brush treatment underneath.

FAA-H-8083-30B, General, printed 8-19, PDF 343

• Prompt and complete correction of a magnesium protective-coating failure is imperative to avoid serious structural damage.
• For magnesium, limit mechanical cleaning to stiff hog-bristle brushes and similar nonmetallic tools, including nonwoven abrasive pads.
• Never use steel or aluminum tools, steel, bronze or aluminum wool, or pads previously used on another metal to clean magnesium.
• Steel wire brushes, carborundum abrasives and steel cutting tools must not be used in the magnesium treatment sequence.
• Advisory Circular (AC) 43.13-1B warns that cuttings and small shavings from magnesium can ignite easily and are an extreme fire hazard.
• Do not let excess magnesium-treatment solution dry on the surface, because the deposits cause paint lifting; restore the original protective paint as soon as dry.
• Extensive removal from a structural magnesium casting may need a manufacturer decision on remaining strength; refer to the structural repair manual whenever safety is in question.
• Steel wool, iron scrapers and steel brushes are prohibited for cleaning or corrosion removal on titanium.
• The handbook’s titanium hand-polishing treatment permits aluminum polish or mild abrasive only with fiber brushes and subsequent sodium-dichromate treatment; wipe off excess solution with dry cloths, without a water rinse.
• AC 43.13-1B prohibits chlorinated hydrocarbon solvents and chemical corrosion removers on titanium and titanium alloys.

FAA-H-8083-30B, General, printed 8-19, PDF 343 · FAA-H-8083-30B, General, printed 8-20, PDF 344 · AC 43.13-1B with Change 1, printed 6-31, PDF 301 · AC 43.13-1B with Change 1, printed 6-38, PDF 307

Restore protection and check the result

• Even negligible corrosion damage needs cleaning, treatment and painting as appropriate.
• For aluminum being refinished, restore the recommended permanent coatings under manufacturer procedures and paint immediately after surface treatment.
• Ensure corrosion treatment is accomplished or reapplied on the same day as scheduled paint refinishing.
• Chromic-acid treatment must receive regular paint as soon as practicable and never later than the day of the latest treatment.
• Store chromium trioxide away from organic solvents and other combustibles, and thoroughly rinse or dispose of chromic-acid wiping cloths.
• Thoroughly rinse cloths and sponges used with commercial activated chromate-acid treatments to avoid a possible fire hazard after drying.
• Chemical cleaners must be used with great care on assembled aircraft because corrosive materials can be entrapped in faying surfaces and crevices; all residues must be removed, since soluble salts from chemical surface treatments liquefy and promote blistering in the paint coatings.
• Our final review: identify the treated location, compare remaining dimensions with the applicable limits, and explain which protective finish was restored.

FAA-H-8083-30B, General, printed 8-20, PDF 344 · FAA-H-8083-30B, General, printed 8-18, PDF 342 · FAA-H-8083-30B, General, printed 8-22, PDF 346 · FAA-H-8083-30B, General, printed 8-23, PDF 347 · FAA-H-8083-30B, General, printed 8-29, PDF 353

Common rehearsal mistakes

• Our checklist: avoid sanding before identifying the metal and finish, sharing dirty pads between metals, accepting pit appearance as a depth limit, or stopping when bare metal merely looks bright.
• Avoid carborundum papers, especially on aluminum or magnesium; emery paper or crocus cloth can cause serious corrosion of those metals by embedded iron oxide.
• Blast cleaning with abrasive media is not applicable to thin aluminum sheet, particularly Alclad; do not use steel grit on aluminum or corrosion-resistant metals.

FAA-H-8083-30B, General, printed 8-29, PDF 353 · FAA-H-8083-30B, General, printed 8-22, PDF 346

For examiner fees and planning, read the DME exam cost guide.

Related guides

• Corrosion Control Oral Exam Questions and Answers
• Sheet Metal Structures Oral Exam Questions and Answers
• A&P Practical Projects: What the DME Evaluates on the O&P

Sources

Primary sources checked October 20, 2026.

• FAA-S-ACS-1
• FAA-H-8083-30B, General
• AC 43.13-1B with Change 1
• FAA Mechanic Test Generator FAQs, updated May 22, 2023
• Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929
• FAA sample oral and practical test

About this guide: drafted with AI from the FAA sources listed on this page and checked claim by claim against them. Not reviewed by an A&P mechanic or DME. How we make our guides