20 Substrate Assessment & Paint Removal Practice Questions & Answers

Every Substrate Assessment & Paint Removal practice question from the ASE B2 Painting & Refinishing Practice Test, with the correct answer and a short explanation.

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1. A car arrives with road film and an old wax coating on the fender to be repaired. Which sequence correctly prepares the area before any sanding begins?
- A.Sand the damage first, then wipe off the dust with wax and grease remover
- B.Blow off loose dirt with air, then sand while the wax still lubricates
- C.Wash with soap and water, then wipe with wax and grease remover✓ Answer
- D.Wipe with wax and grease remover, then wash with soap and water
Soap and water removes water-soluble dirt and grime first, and wax and grease remover then dissolves wax, oils and silicone; both must happen before sanding, because sanding over wax or silicone drives it into the scratches and causes fisheyes later.
Ref QB-QUBX92Source: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Surface Preparation: removing contaminants)Report a problem with this question
2. Painter A says wax and grease remover should be wiped on and then left to evaporate completely on the panel so it can lift the contaminants. Painter B says the panel should be sanded first and cleaned afterward, because sanding cuts through the wax. Who is right?
- A.Both A and B
- B.A only
- C.B only
- D.Neither A nor B✓ Answer
Both are wrong. The remover must be wiped off with a clean, dry cloth while it is still wet (two-cloth method); if it flashes off, the dissolved contaminant is simply redeposited. Cleaning must come before sanding, since sanding over wax or silicone grinds it into the scratches.
Ref QB-6CTEHYSource: I-CAR refinish training principles: surface cleaning with the two-cloth method before sandingReport a problem with this question
3. After a body side emblem is removed, a band of adhesive residue remains on the sound clearcoat. Which removal method is most appropriate?
- A.An adhesive remover or a rubber eraser wheel✓ Answer
- B.A grinder with a coarse disc, so the residue is cut off in one quick pass
- C.Soap and water alone, since adhesive is water-soluble like road grime
- D.A steel putty knife scraped flat, since the clear is hard enough to resist it
Adhesive residue is not water-soluble, and aggressive abrasives or steel scrapers damage a finish that is otherwise sound. A dedicated adhesive remover or a rubber eraser wheel lifts the residue without cutting into the clearcoat.
Ref QB-PUYK4ZSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (removing adhesive residue and other contaminants)Report a problem with this question
4. A new, unpainted plastic bumper cover may still carry mold release agent from the factory. What is the correct way to prepare its surface?
- A.Strip it with chemical stripper to dissolve the release agent fully
- B.Rinse with plain water only, since any cleaner will attack the plastic
- C.Clean with a plastic cleaner, scuff the surface, then clean it again✓ Answer
- D.Sand it with a coarse grit so the scratches cut through the release agent
Mold release is a waxy contaminant; cleaning first keeps it from being sanded into the surface, scuffing gives a mechanical key, and the second cleaning removes what the scuffing loosened. Chemical stripper damages plastics, and coarse sanding only embeds the release agent.
Ref QB-9CVE24Source: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (removing mold release agents)Report a problem with this question
5. Painter A says a phosphoric-acid metal conditioner should be applied to rusty bare steel before plastic body filler is spread over it. Painter B says body filler should go over clean, bare metal that has been sanded until all the rust is gone. Who is right?
- A.A only
- B.Both A and B
- C.B only✓ Answer
- D.Neither A nor B
Metal conditioner is not used under plastic body filler, even where rust was present; its residue interferes with filler adhesion. The rust must be removed mechanically to bright metal and the filler applied over clean, sanded bare metal.
Ref QB-SU2MM4Source: ASE Collision Repair and Refinish Study Guide, Test B2 sample questions and task list (identify and remove surface corrosion)Report a problem with this question
6. After DA sanding a rusty chip on a steel door, small dark pits of rust remain below the sanded surface. What is the best next step?
- A.Leave the pits, since the topcoat will isolate them from new moisture
- B.Media blast the pits to bright metal, then treat and protect the steel✓ Answer
- C.Bury the pits under primer-surfacer, which seals out air and moisture
- D.Fill the pits with body filler, which locks out oxygen and halts the rust
Any rust left in pits keeps growing under new coatings and eventually lifts or blisters the finish. Pits that sanding cannot reach are cleaned by media blasting (and treated with metal conditioner where appropriate) until bright metal shows, then protected with a corrosion-resistant undercoat.
Ref QB-8CH4V2Source: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (identify and remove surface corrosion)Report a problem with this question
7. All of these are acceptable practices when removing surface corrosion from an aluminum hood EXCEPT:
- A.Using a carbon steel wire brush that is shared with steel repairs✓ Answer
- B.Using sanding discs that have never been used on steel panels
- C.Priming the bare aluminum soon after sanding to limit new oxide
- D.Using a stainless steel brush reserved only for aluminum work
Steel particles left embedded in aluminum set up galvanic corrosion, so tools and abrasives used on steel must never be used on aluminum. Dedicated stainless brushes and clean abrasives are acceptable, and prompt priming matters because aluminum oxide re-forms quickly.
Ref QB-RUP9F3Source: I-CAR aluminum repair and refinish principles: dedicated tools to prevent galvanic corrosionReport a problem with this question
8. A painter sands a small test spot on a car of unknown history, and the sandpaper loads with white residue rather than the car's color. What type of finish is this most likely?
- A.A single-stage metallic finish
- B.An oxidized single-stage enamel
- C.A single-stage solid color
- D.A basecoat/clearcoat finish✓ Answer
Clearcoat contains no pigment, so sanding it produces white dust; a single-stage finish carries pigment at the surface, so sanding or polishing it leaves the vehicle's color on the paper or pad, whether the finish is solid, metallic or oxidized.
Ref QB-3CREZUSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (inspect and identify type of finish)Report a problem with this question
9. A painter rubs lacquer thinner on an inconspicuous spot of a vehicle's old finish, and the paint softens and smears. What does this indicate, and what should the refinish plan include?
- A.A solvent-sensitive finish; seal it or strip it before refinishing✓ Answer
- B.A sound basecoat/clearcoat; wet sand it and add more clear on top
- C.A dirty surface; rewash it with soap and water and then proceed
- D.A fully cured 2K urethane; scuff it and refinish directly over it
A finish that dissolves or softens under lacquer thinner is lacquer or another air-dry, solvent-sensitive coating. Strong refinish solvents will make it lift or wrinkle, so the plan must isolate it with a sealer or remove it; a cured 2K finish would resist the thinner.
Ref QB-KUWKKVSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (inspect type of finish; develop a refinishing plan)Report a problem with this question
10. All of these findings during inspection call for removing the old finish before refinishing EXCEPT:
- A.A finish that softens and lifts when tested with lacquer thinner
- B.A finish that is well bonded and intact but dull from weathering✓ Answer
- C.A finish that is peeling and shows poor adhesion to the layer below
- D.A paint gauge reading far above factory film build, with fine cracks
A finish that is sound and well bonded, even if weathered, can be sanded and refinished over. Excessive film build with cracking, solvent sensitivity and poor adhesion all mean the old film is an unstable base, so it must be removed down to a sound substrate.
Ref QB-8UQJGFSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (inspect film thickness and surface condition; remove paint finish)Report a problem with this question
11. Painter A says that if a magnet will not stick to a body panel, the panel may be aluminum or a plastic or composite part. Painter B says the substrate type determines which surface treatment and undercoat will be used. Who is right?
- A.Neither A nor B
- B.A only
- C.Both A and B✓ Answer
- D.B only
Both are right. Steel is magnetic, while aluminum, plastics and composites are not, so a magnet is a quick first check. Identifying the substrate matters because steel, galvanized steel, aluminum and plastic each need different cleaning, abrasives, treatment and undercoats.
Ref QB-QBJDWESource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (inspect and identify substrate)Report a problem with this question
12. All of these are correct practices when using a chemical paint stripper on a steel panel EXCEPT:
- A.Letting it run onto the plastic bumper to soften that paint too✓ Answer
- B.Masking seams and openings so the stripper cannot seep inside
- C.Wearing chemical-resistant gloves and eye and face protection
- D.Neutralizing and cleaning the bare metal as the label directs
Chemical stripper attacks plastics and the resin in fiberglass and composites, so it must be kept off and away from those parts. Masking crevices, wearing proper PPE and neutralizing or cleaning per the label are all required steps.
Ref QB-9U3WNGSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (remove paint finish); product Safety Data Sheet practiceReport a problem with this question
13. A thin-gauge steel hood must be stripped to bare metal over its whole surface. Which method is best suited to this job?
- A.Grinding with a coarse disc, which is faster than any blasting method
- B.Plastic media blasting at low pressure, which won't warp the metal✓ Answer
- C.Steel shot blasting, which leaves a deep anchor pattern for the primer
- D.Sand blasting at high pressure, which strips the most paint per minute
Plastic media removes paint without heating, stretching or eroding thin sheet metal. Sand and steel shot are aggressive enough to warp and stretch thin panels and belong on heavy-gauge parts, and grinding a whole hood builds heat and removes metal.
Ref QB-RBWQ3GSource: I-CAR refinish training principles: paint removal methods (media blasting)Report a problem with this question
14. Painter A says grinding with a coarse disc builds heat that can warp a thin panel, so the disc must be kept moving. Painter B says sand blasting is the preferred way to strip thin aluminum panels. Who is right?
- A.Both A and B
- B.A only✓ Answer
- C.B only
- D.Neither A nor B
Only A is right. Concentrated grinding heat distorts thin sheet metal, so a light touch with a moving disc is required. Sand blasting is too aggressive for thin panels, especially soft aluminum; low-pressure plastic media is used instead.
Ref QB-AUE8UHSource: I-CAR refinish training principles: paint removal methods and their effect on thin panelsReport a problem with this question
15. After basecoat and clearcoat are applied over a repair, fine sand scratches become visible in the finish. What is the most likely cause?
- A.Deeper scratches from a coarser grit were not removed by the next grit✓ Answer
- B.Wax and grease remover was used after sanding instead of before it
- C.The area was block sanded instead of being finished with a DA sander
- D.The final grit was too fine to give the topcoat a mechanical bite
Each grit must completely remove the scratches of the one before it; jumping too far between grits or stopping early leaves deep scratches that swell with topcoat solvents and show through. A grit that is too fine causes adhesion problems, not visible scratches.
Ref QB-SB939HSource: I-CAR refinish training principles: sanding grit progression and sand-scratch swellingReport a problem with this question
16. Painter A says dry sanding with dust extraction is the preferred method on body filler and bare steel. Painter B says body filler should be wet sanded to keep the dust down. Who is right?
- A.Neither A nor B
- B.Both A and B
- C.B only
- D.A only✓ Answer
Only A is right. Body filler is porous and absorbs water, which later causes blistering and corrosion under the finish, and water on bare steel causes flash rust. Dry sanding with dust extraction controls the dust without those risks.
Ref QB-BUSJZJSource: I-CAR refinish training principles: dry sanding with dust extraction on filler and bare metalReport a problem with this question
17. When an area of broken paint has been properly featheredged, how should the edge of the old finish look?
- A.A sharp, square step between paint and bare metal that primer can fill
- B.Each paint layer shows as a wide, distinct ring around the bare metal✓ Answer
- C.All paint is removed back to the nearest panel edge, leaving bare metal
- D.The layers merge into one narrow band of a single, uniform color
A good featheredge is a long, gradual taper, so clear, base, primer and e-coat each appear as a separate wide band (a bull's-eye). A hard step or a narrow band means too little taper, and that edge will show through the topcoat as a ring.
Ref QB-TBMDEJSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (featheredge areas to be refinished)Report a problem with this question
18. While a painter featheredges and primes a repair, the edge of the old finish lifts and wrinkles. What is the most likely cause, and what is the correct fix?
- A.The featheredge is too wide; narrow it so the primer touches less paint
- B.The primer film is too thin; apply heavier coats to bury the edge
- C.The old finish is solvent-sensitive; isolate it with a sealer or remove it✓ Answer
- D.The DA was tilted too far; keep sanding the edge with a finer grit
Lifting and wrinkling at a featheredge happen when solvents in the new material attack a solvent-sensitive old finish such as lacquer. More sanding or heavier coats make it worse; the finish must be isolated with a sealer or removed.
Ref QB-CU5W6MSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (featheredge areas; inspect type of finish)Report a problem with this question
19. Painter A says tilting the DA sander onto its edge is the best way to featheredge quickly. Painter B says a hard, poorly tapered edge may show through the topcoat as a ring. Who is right?
- A.A only
- B.Both A and B
- C.Neither A nor B
- D.B only✓ Answer
Only B is right. The DA must be kept flat; tilting it concentrates the cut, digs gouges and leaves an uneven edge. An edge without enough taper telegraphs through the finish as a visible ring or edge mapping.
Ref QB-UBYQKKSource: I-CAR refinish training principles: featheredging techniqueReport a problem with this question
20. A painter levels a long, gently curved body line using only a DA sander. After primer-surfacer and a guide coat, low waves are still visible along the line. What is the most likely cause?
- A.The grit was too coarse, so the DA cut the low spots deeper than the highs
- B.The guide coat was too heavy and filled the low spots with powder
- C.The primer-surfacer shrank because it was sanded with a block too soon
- D.The DA pad followed the contour instead of cutting the high spots flat✓ Answer
A soft DA pad rides up and down with the surface, so it removes material evenly without leveling. A long block bridges the low spots and cuts the high spots first, and the guide coat shows where the surface is still high or low.
Ref QB-HCNPP5Source: I-CAR refinish training principles: block sanding versus DA sanding and guide coat useReport a problem with this question

1. A car arrives with road film and an old wax coating on the fender to be repaired. Which sequence correctly prepares the area before any sanding begins?

2. Painter A says wax and grease remover should be wiped on and then left to evaporate completely on the panel so it can lift the contaminants. Painter B says the panel should be sanded first and cleaned afterward, because sanding cuts through the wax. Who is right?

3. After a body side emblem is removed, a band of adhesive residue remains on the sound clearcoat. Which removal method is most appropriate?

4. A new, unpainted plastic bumper cover may still carry mold release agent from the factory. What is the correct way to prepare its surface?

5. Painter A says a phosphoric-acid metal conditioner should be applied to rusty bare steel before plastic body filler is spread over it. Painter B says body filler should go over clean, bare metal that has been sanded until all the rust is gone. Who is right?

6. After DA sanding a rusty chip on a steel door, small dark pits of rust remain below the sanded surface. What is the best next step?

7. All of these are acceptable practices when removing surface corrosion from an aluminum hood EXCEPT:

8. A painter sands a small test spot on a car of unknown history, and the sandpaper loads with white residue rather than the car's color. What type of finish is this most likely?

9. A painter rubs lacquer thinner on an inconspicuous spot of a vehicle's old finish, and the paint softens and smears. What does this indicate, and what should the refinish plan include?

10. All of these findings during inspection call for removing the old finish before refinishing EXCEPT:

11. Painter A says that if a magnet will not stick to a body panel, the panel may be aluminum or a plastic or composite part. Painter B says the substrate type determines which surface treatment and undercoat will be used. Who is right?

12. All of these are correct practices when using a chemical paint stripper on a steel panel EXCEPT:

13. A thin-gauge steel hood must be stripped to bare metal over its whole surface. Which method is best suited to this job?

14. Painter A says grinding with a coarse disc builds heat that can warp a thin panel, so the disc must be kept moving. Painter B says sand blasting is the preferred way to strip thin aluminum panels. Who is right?

15. After basecoat and clearcoat are applied over a repair, fine sand scratches become visible in the finish. What is the most likely cause?

16. Painter A says dry sanding with dust extraction is the preferred method on body filler and bare steel. Painter B says body filler should be wet sanded to keep the dust down. Who is right?

17. When an area of broken paint has been properly featheredged, how should the edge of the old finish look?

18. While a painter featheredges and primes a repair, the edge of the old finish lifts and wrinkles. What is the most likely cause, and what is the correct fix?

19. Painter A says tilting the DA sander onto its edge is the best way to featheredge quickly. Painter B says a hard, poorly tapered edge may show through the topcoat as a ring. Who is right?

20. A painter levels a long, gently curved body line using only a DA sander. After primer-surfacer and a guide coat, low waves are still visible along the line. What is the most likely cause?

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