Fifteen years of target life is the headline. What decides whether a tank passes is thickness, stripe coats, salt limits and the paperwork.
A shipyard quotes a ballast tank coating job and the owner asks whether it is PSPC compliant. The yard says yes, the product is approved. That answer covers perhaps a third of what the standard actually requires, and the rest of it is where tanks fail at delivery.
What the standard applies to
The Performance Standard for Protective Coatings was adopted by the IMO to stop ballast tanks from corroding through in the first decade of a ship's life.
- It covers dedicated seawater ballast tanks on all ship types of 500 gross tonnage and above, and double-side skin spaces of bulk carriers.
- It sets a target useful life of fifteen years, with the coating expected to remain in good condition at that age.
- It is not a product approval alone. The standard governs surface preparation, the coating system, the inspection regime, the qualifications of the inspector, and the documentation that must be delivered with the ship.
- It applies at new construction and at repair. Maintenance work on a PSPC tank is expected to restore the coating to the standard, under separate guidelines.
The technical requirements that get checked
- Surface preparation to Sa 2½ with a defined profile, typically 30 to 75 microns depending on the system.
- Soluble salt limit, measured before the first coat. This is a number, not an opinion, and it is one of the most common non-conformities.
- Epoxy-based system. The standard names the acceptable binder families and excludes alkyd, acrylic, chlorinated rubber and water-borne systems for this service.
- Nominal dry film thickness of 320 microns for the epoxy system, achieved as a specified number of coats.
- Stripe coats on all edges, welds, cutouts and difficult areas, applied before the main coat and in a contrasting colour.
- A qualified coating inspector holding a recognised certification at the required level, independent of the coating applicator.
- A Coating Technical File containing the specification, the product data, the inspection records and the statement of compliance.
The 80/20 rule is where most arguments start
PSPC thickness measurement uses a statistical rule, and misunderstanding it causes more delivery disputes than the coating itself.
- All measured thicknesses must be at or above 80 percent of the nominal thickness. A reading below that is not a pass with a note; it is a defect to be repaired.
- At least 80 percent of the readings must be at or above the nominal thickness. The average being above nominal does not compensate for a cluster of thin readings.
- Measurement follows a defined procedure on rough surfaces, which means the instrument and the correction method matter. A gauge reading on a blasted surface is not directly the dry film thickness without the appropriate adjustment.
- Destructive testing has its own rules. Where it is used, the test points are repaired afterwards, and the repair is inspected like the original.
The salt limit and why it is enforced
Blasting does not remove soluble salts from the bottom of the profile. If chlorides remain, water passes through the coating, dissolves them, and the osmotic pressure lifts the film.
- The measurement is taken on the prepared surface, before the first coat, by a recognised field method.
- A failed salt reading means re-cleaning, not a thicker coat. No amount of epoxy compensates for a contaminated interface in a ballast tank.
- The record goes in the Coating Technical File. The file is reviewed at delivery, and an incomplete record can hold up the ship.
Where the practical difficulty sits
- Block stages. Much of the coating is applied in blocks, then damaged during assembly. The repair of that damage has to meet the same standard, and it is the area most often done quickly and badly.
- Stripe coats are labour-intensive. Every edge, weld and cutout needs a brush pass. It is the first activity cut when the schedule slips, and it is the one that decides whether the tank reaches fifteen years.
- Cure time versus dock time. A 320 micron epoxy at low temperature needs time. Compressing the cure to keep the dock schedule is the classic cause of a tank that passes thickness and fails adhesion.
- Inspector availability. A qualified inspector has to be present at the defined hold points. This is a planning constraint, not a formality.
What owners should ask for
- The Coating Technical File, not a certificate for the product.
- Thickness records by area, with the measurement method, not a single average figure.
- Salt test results with date, location and method.
- Photographs of stripe coats before the full coat, and of the completed tank.
- The inspector's certification and the hold point records they signed.
Beyond compliance
A tank can be fully compliant and still disappoint. The standard sets a floor for preparation, material family and inspection, and it does not control how carefully the work is done inside those limits.
What separates a tank that lasts fifteen years from one that needs major work at ten is usually not the product. It is whether the stripe coats were done on every edge, whether the salt was actually measured, whether the film was given time to cure, and whether anyone kept the records that would let the next repair match the original system.