Pitted Plate Assessment Tool Hull Pitting Calculator for Vessel Owners
Calculation results will be displayed here after running the assessment.
The Pitted Plate Assessment Tool (PPAT) is a free resource developed by a joint USCG/PVA working group to help commercial vessel owners and operators evaluate hull pitting damage, estimate remaining plate integrity, and document findings before a Coast Guard inspection. Built on the methodology of Ship Structure Committee report SSC-394 (Strength Assessment of Pitted Plate Panels), this tool gives you a defensible, data-backed assessment of your vessel's condition — whether you're monitoring isolated aluminum hull pitting or managing more widespread corrosion across steel plating.
Hull pitting is localized corrosion that creates small craters or depressions in a vessel's metal plating. Left unmonitored, pitting progressively reduces plate thickness. Once it falls below the minimum allowable level, the plate is no longer structurally adequate — leading to costly drydock repairs, plate replacement, or a vessel being taken out of service by the United States Coast Guard (USCG).
Pitting is especially common on aluminum hull vessels operating in salt water environments, where galvanic corrosion accelerates material loss. On steel hulls, isolated pitting can go unnoticed during routine visual inspections until the damage is severe. As SSC-394 notes, borderline cases were historically treated conservatively — plates were replaced even when only marginally degraded. Today, with tighter operating margins, unnecessary "crop and renew" repairs are a significant cost burden. Equally, underestimating pitting severity creates real structural and regulatory risk.
The U.S. Coast Guard periodically inspects commercial passenger vessels and evaluates hull pitting using direct measurement of pit depth and diameter. If pitting is deemed severe enough to require plate replacement, the expense can be substantial.
Having your own documented assessment — based on the same underlying SSC-394 methodology used by USCG inspectors — puts you in a much stronger position to discuss findings, propose alternatives to full plate replacement, and support a repair proposal.
The PPAT is based on Ship Structure Committee report SSC-394, SR-1356: Strength Assessment of Pitted Plate Panels (1997), developed under the direction of Rear Admiral J.C. Card, U.S. Coast Guard Chairman of the Ship Structure Committee. The original SSC-394 "PIT" program was designed as a field tool for inspectors to evaluate pitted plating on scene by recording a small number of measurable parameters and calculating the probability that plate strength has fallen below acceptable limits.
The Passenger Vessel Association's Director of Regulatory Affairs, Eric P. Christensen, worked with a USCG/PVA working group to adapt this methodology into the web-based PPAT, making it accessible to vessel owners and operators throughout the country — particularly those engaged in appeals and reconsideration processes with USCG sectors regarding base metal repair approvals.
If your vessel is subject to USCG inspection under 46 CFR Subchapter H or K, hull pitting will be evaluated at drydocking.
Having a recent, documented PPAT assessment allows you to:
This tool does not replace the judgment of a qualified marine surveyor or Coast Guard inspector, and results should be used as one input among several in preparing for inspection or repair discussions. After running the assessment, email the results directly to yourself for your records.
Follow these steps before entering data. All inputs should be in millimeters — use the built-in inches-to-mm converter if your measurements are in inches. When judgment calls are required (steps 2 and 5), all inspecting personnel should agree on the values before entering them.
Per SSC-394, locate a 300 mm x 300 mm (12 in x 12 in) area of the pitted panel that visually represents the full panel in terms of pitting intensity, depth, and diameter. Mark the boundary with chalk. A rectangular sample can be used if needed — uncheck the square checkbox in the tool to enter separate width and height values.
Count all pits within the marked sample area and enter this number as the Frequency input.
Identify the pit you judge to have the average depth for the sample area. Measure it and enter as Average Depth (mm).
Find and measure the deepest pit in the sample area. Enter as Maximum Depth (mm).
Identify the pit you judge to have the average diameter for the sample area (this does not need to be the same pit used for average depth). Enter as Average Diameter (mm).
Measure the widest pit in the sample area (does not need to be the same pit used for maximum depth). Enter as Maximum Diameter (mm).
Enter the width and height of your sample area. Default is 300 × 300 mm per SSC-394 recommendations.
Enter the original plate thickness in mm.
Click Run Calculation. The calculation may take up to 3 minutes. Once complete, you can email the results to yourself for documentation.
This pitting assessment software is provided for public use by the Passenger Vessel Association (PVA) as a vessel maintenance tool to monitor isolated hull pitting and integrity. Users are solely responsible for the accuracy of the input of data as well as the resulting accuracy of all assessments.
As a result, PVA is not liable for any errors, omissions, or damages resulting from the imprecise, inexact, or inaccurate use of this software.
© 2026 Passenger Vessel Association
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