AMPP Senior Corrosion Technologist common mistakes
AMPP Senior Corrosion Technologist · Understand the traps and how to avoid them.
When sizing galvanic anodes, selecting anode output by reading the open-circuit potential rather than the closed-circuit (driving) potential, so calculated current is far too high.
The open-circuit potential is the value most often tabulated and remembered, and it is easy to substitute it for the polarized structure-to-anode potential difference without noticing.
What to do instead
Always compute anode current from the closed-circuit driving voltage (anode potential minus protected structure potential, typically -0.85 V CSE for steel), and state the assumed structure potential explicitly in the calculation.
Treating a structure-to-electrolyte potential of -0.85 V CSE as a universal criterion regardless of environment, temperature, or presence of sulfate-reducing bacteria.
The -0.85 V figure is the most memorized number in cathodic protection and is recalled without its qualifying conditions.
What to do instead
Apply the 100 mV polarization criterion or the -0.85 V criterion with awareness of anaerobic/bacterial conditions (commonly -0.95 V CSE) and temperature effects; state which criterion is being applied and why.
On coating failure questions, attributing blistering or disbondment to a single cause instead of distinguishing osmotic blistering, cathodic disbondment, and solvent entrapment by their signature appearance and location.
All three present as coating loss, and candidates pattern-match to the most recently studied mechanism.
What to do instead
Build a decision table: osmotic blistering shows solute-concentration-driven domes with liquid inside; cathodic disbondment radiates from holidays or edges on cathodically protected steel; solvent entrapment shows solvent-smell blisters shortly after application. Match the described evidence before choosing.
Confusing the roles of surface preparation standard and coating selection when asked why a coating failed prematurely, blaming the coating when the described profile or cleanliness was inadequate.
Coating chemistry is more visually memorable than abrasive blast grade designations, so candidates overweight the product.
What to do instead
For any coating failure scenario, first check the stated surface preparation (blast grade, profile depth, salt contamination, dew point) against the coating's data sheet before evaluating the coating itself.
Assuming stainless steel is immune to corrosion in all service conditions, missing chloride stress corrosion cracking or pitting in the described environment.
Stainless steels are taught as 'corrosion resistant', and candidates carry that label into aggressive chloride or elevated-temperature scenarios.
What to do instead
Whenever a stainless alloy appears in a question, check three things: chloride concentration, temperature (SCC risk rises above roughly 60 C for 300-series), and oxygen availability for pitting; flag sensitization if welding is mentioned.
Mixing up the direction of galvanic coupling, predicting that the more active (anodic) metal in a couple is protected when it is actually the one that corrodes faster.
The word 'protection' in cathodic protection training creates confusion about which member of a couple is the cathode.
What to do instead
Anchor on the galvanic series: the more negative (active) member becomes the anode and corrodes; the more noble member becomes the cathode and is protected. Rehearse this with a dissimilar-metal couple example before answering.
When asked to select or dose a chemical treatment, choosing the treatment type by name recognition rather than matching the mechanism to the described corrosion morphology (e.g., oxygen scavenger for CO2 corrosion).
Treatment chemicals are learned as a list, and exam items describe symptoms rather than naming the mechanism.
What to do instead
Map morphology to mechanism first: sweet (CO2) corrosion gives uniform/grooved attack, sour (H2S) gives sulfide scaling and cracking risk, oxygen gives pitting. Then select the treatment whose mechanism addresses that specific corrosive species.
Ignoring the interaction between chemical treatment and other control methods, such as a corrosion inhibitor that is incompatible with the biocide program or that partitions poorly into the water phase.
Each control method is studied in isolation, so compatibility and partitioning questions feel unfamiliar.
What to do instead
For any treatment question, ask three compatibility questions: phase partitioning (oil vs water), interaction with other injected chemicals, and effect on downstream processes; eliminate options that ignore these.
On internal corrosion items, failing to identify the water-wetting and accumulation locations (low spots, dead legs, slug flow regimes) and instead answering based on general metal loss rates.
Internal corrosion is taught through mechanisms, but exam items test whether the candidate can locate where the mechanism will act.
What to do instead
Before selecting a mechanism, identify the phase behavior and geometry described: where does free water settle, where is flow stratified, which lines are stagnant. Location drives mechanism selection.
In safety planning, writing a hazard response that names PPE or a permit but omits the specific exposure scenario, monitoring, and rescue/emergency element the question is testing.
Candidates default to generic safety language because confined-space and H2S items feel like common sense rather than technical content.
What to do instead
Structure every safety answer as: hazard identified, exposure route, engineering control, monitoring method, PPE, and emergency/rescue plan. If an option lacks the monitoring or rescue element, it is usually the wrong choice.