ABYC Marine Corrosion Exam Study Guide (2026)
Everything the ABYC Marine Corrosion Certification Exam tests, topic by topic: what each section covers, the facts that come up most, and how to study it. Pair it with the free 15-question practice test.
The exam at a glance
| Questions | 189 multiple-choice questions |
|---|---|
| Time | 3.5 hours |
| Passing score | 83.6% (ABYC's published cut score) |
| Format | Proctored, computer-based multiple choice; reference-material rules are not stated on the public exam pages, so confirm them when you book |
| Certifying body | American Boat & Yacht Council (ABYC) |
| Test provider | Online with a remote proctor (webcam, microphone, Chrome, government ID, single monitor), or at the end of an ABYC certification class |
Mind map: the whole exam on one screen
Read the complete ABYC Marine Corrosion study notes for “Corrosion Chemistry and Electrical Theory”
Our first full set of comprehensive notes, about 13 minutes of reading: The corrosion cell · Oxidation and reduction · pH and the electrolyte · Conventional flow and electron flow, a worked exam example, the traps examiners use and a one-minute recap. Create a free account to read it and see how premium notes work before you decide.
1. Corrosion Chemistry and Electrical Theory
Atoms, ions, oxidation and reduction, pH, and conventional versus electron flow: the science behind every corrosion question.
Key facts
- Corrosion is an electrochemical reaction: it needs an anode, a cathode, an electrolyte and a metallic path between anode and cathode.
- Oxidation (loss of electrons) happens at the anode, which loses metal. Reduction (gain of electrons) happens at the cathode, which is protected.
- Remove any one of the four elements of the cell and corrosion stops: that's the basis of coatings, isolation and cathodic protection.
- pH measures acidity: 7 is neutral, below 7 acidic, above 7 alkaline. Seawater is slightly alkaline.
- Conventional current flows positive to negative in the external circuit; electrons flow negative to positive.
- Seawater is a better electrolyte than fresh water (lower resistivity), so corrosion currents are larger in salt water.
Flashcards
Exam tip: When stuck, draw the cell: anode, cathode, water, wire. Then ask which part the question is changing.
2. The Galvanic Series and Galvanic Corrosion
The galvanic series in seawater, what drives galvanic corrosion, and why area ratios and distance matter.
Key facts
- The galvanic series ranks metals by potential in seawater (against silver/silver chloride). Magnesium is most anodic, then zinc and aluminum alloys; graphite and passive stainless and titanium are near the noble end.
- When two different metals are connected in an electrolyte, the more anodic one corrodes faster and the more noble one is protected.
- The larger the potential difference between the metals, the greater the driving force.
- Area ratio: a small anode connected to a large cathode corrodes rapidly. A large anode with small cathodes corrodes slowly.
- Stainless steel has two positions in the series: passive (oxide film intact, noble) and active (film broken down, much less noble).
- Galvanic corrosion needs both electrical contact and an electrolyte between the metals.
Flashcards
Exam tip: Area-ratio questions are easy points once you know the rule. Find the small part and ask whether it's the anode.
3. Stray Current and Shore Power
DC and AC stray current, shore power grounding, galvanic isolators (A-28) and isolation transformers.
Key facts
- Stray-current corrosion happens where current leaves a metal and enters the water; it can be far faster than galvanic corrosion.
- Common sources: a DC positive conductor leaking into bilge water, a faulty device, or current arriving through the shore grounding conductor.
- The shore power green conductor connects your boat's underwater metals to every other boat on the dock, creating galvanic paths.
- A galvanic isolator in the green conductor blocks low-voltage DC galvanic current while still passing AC fault current.
- An isolation transformer breaks the metallic connection between the shore grounding conductor and the boat, so no galvanic isolator is needed.
- The AC neutral must never be connected to ground aboard while on shore power: that puts return current on the grounding system.
Flashcards
Exam tip: Rapid loss of anodes or fittings after a new installation or at a new marina usually points to stray or shore current, not ordinary galvanic action.
Test yourself on these topics
Take the free 15-question ABYC Marine Corrosion test, then save your results to unlock your Readiness Score and the mistakes bank.
4. Cathodic Protection and Anodes
ABYC E-2 cathodic protection: sacrificial anodes, impressed current systems, protection criteria and choosing anode materials.
Key facts
- Cathodic protection makes the metals you want to save the cathode of the cell, supplying current from a sacrificial anode or an impressed current system.
- E-2 requires a minimum 200 mV negative shift from the freely corroding potential of the least noble metal being protected.
Flashcards
Exam tip: Learn the anode-water pairs as a table: salt = zinc or aluminum, brackish = aluminum, fresh = magnesium.
5. Metals, Aluminum Boats and Coatings
How common marine metals behave, T-1 aluminum applications, crevice corrosion of stainless, and protective coatings.
Key facts
- Aluminum is amphoteric: it corrodes in strong acid and in strong alkali, which is why overprotection harms it.
- Copper-based antifouling must not be used on aluminum hulls; any break in the coating creates a galvanic cell with the hull as anode.
Flashcards
Exam tip: Questions that mention "stagnant", "under a seal" or "in wet wood" with stainless steel are pointing at crevice corrosion.
6. Corrosion Surveys
How to carry out a corrosion survey: equipment, readings, comparing against the E-2 ranges and finding the source.
Key facts
- Equipment: a digital meter with high input impedance and a silver/silver chloride reference electrode in the water near the boat.
- Readings are taken between the reference electrode and the boat's bonding system or individual underwater metals.
Flashcards
Exam tip: Survey questions reward method: change one thing at a time and compare. The answer that isolates a single variable is usually right.
How to pass
- 189 questions in 3.5 hours gives you just over 1 minute each, more time per question than Marine Electrical, Systems or Engines and Fuel Systems. Use it on the scenario questions.
- The cut score is 83.6%: you can miss only about 31 questions.
- Most questions come back to one idea: the anode (the more negative metal) corrodes, and current leaving metal into water removes metal. Reason from that before you guess.
- ABYC assumes you know Marine Electrical material (grounding, bonding, galvanic isolators, shore power). Review it if you haven't taken that exam.
Frequently asked questions
How long should I study for the ABYC Marine Corrosion exam?
Most working candidates need 4 to 8 weeks at 45 to 60 minutes a day. Book your exam once your Readiness Score has stayed at 80 or higher for about a week.
Can I take the ABYC Marine Corrosion exam online?
Yes. ABYC certification exams are taken with a proctor: online through a remote proctoring service, or for some certifications at the end of an ABYC class. Format: proctored, computer-based multiple choice; reference-material rules are not stated on the public exam pages, so confirm them when you book. Ask the ABYC Education Department which reference materials are allowed.
What score do I need to pass the ABYC Marine Corrosion exam?
83.6% (ABYC's published cut score). The exam has 189 multiple-choice questions and a time limit of 3.5 hours.
What are the most tested topics?
The outline covers corrosion chemistry and electrical theory, the galvanic series and galvanic corrosion, stray current and shore power, cathodic protection and anodes, metals, aluminum boats and coatings, corrosion surveys. Use the free practice test to see which ones you need most.
The premium ABYC Marine Corrosion study path
Premium ABYC Marine Corrosion prep is studied one topic at a time. Each step starts with that topic's key notes and flashcard deck, then its own question sets of 25, so you master one topic before you move to the next. When every topic is strong, the 6 full mock exams show you're ready.
Your step-by-step study path
- 1Corrosion Chemistry and Electrical Theory10 key notes, 135 flashcards, then 500 practice questions in 20 sets of 25Notes free with an account
- 2The Galvanic Series and Galvanic Corrosion10 key notes, 135 flashcards, then 500 practice questions in 20 sets of 25Premium
- 3Stray Current and Shore Power10 key notes, 135 flashcards, then 500 practice questions in 20 sets of 25Premium
- 4Cathodic Protection and Anodes10 key notes, 135 flashcards, then 500 practice questions in 20 sets of 25Premium
- 5Metals, Aluminum Boats and Coatings10 key notes, 130 flashcards, then 500 practice questions in 20 sets of 25Premium
- 6Corrosion Surveys10 key notes, 130 flashcards, then 500 practice questions in 20 sets of 25Premium
- Final step: 6 full mock exams189 questions each, timed like test day. Pass them, then book your exam.Premium
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- One ABYC exam of your choice: any of the 10 certifications, from Marine Electrical to USCG Regulations
- 3,000 practice questions + 6 full mock exams per exam
- 800 flashcards + 60 key notes per exam, by topic, plus mind maps
- Spaced repetition + mistakes bank
- Readiness Score & detailed reports
- Video lessons as they release
- Content updates during your access
- 5 bonuses: numbers and formulas sheet, standards map, study planner and more
- Pass Guarantee: complete the prep, pass or 100% back
Renews once a year until you cancel. We email you before each renewal. Cancel any time from your account; you keep access until the end of the year you've paid for.
Summarized from ABYC's official candidate information and the rules cited, checked November 2026. Confirm current requirements with American Boat & Yacht Council (ABYC).