GB/T 34430.4-2024 in English

Background of Standard Development and Technological Evolution

In December 2006, the International Maritime Organization (IMO) officially adopted the Performance Standard for Protective Coatings (PSPC), which, as a mandatory regulation, puts forward higher requirements for ship coating processes. Coating quality depends largely on surface preparation and coating application, so it is crucial to correctly perform surface preparation, coating, and inspection according to the coating manufacturer's recommendations. The development of the GB/T34430.4—2024/ISO16145-4:2013 standard aims to provide standardized guidance for shipowners, shipyards, coating manufacturers, coating inspectors, and coating applicators in the application of PSPC during the new shipbuilding phase.

Measurement Principle and Technical Features

This document describes an automated method for measuring the total surface density of various water-soluble salts on steel surfaces using a conductivity meter. The measurement principle is to fix the detector consisting of a sampling device and electrodes to the steel surface, fix it in place using a magnetic base or tape, use a known volume of water to dissolve and extract the water-soluble salts on the surface of the matrix and in the detector, and then use a conductivity meter to measure the conductivity of the extract to be tested.

This method determines the total concentration of water-soluble ionic contaminants through conductivity testing, thereby quickly assessing whether there is ionic contamination on the steel surface. The measurement results are equivalent to the GB/T18570.9-2005 standard, but cannot be used to determine the individual surface density of chlorides, sulfates, etc., and can only assess the total amount of ionic contaminants.

Instrument and Equipment Technical Requirements

Standardized procedure for measurement steps

6.1 General requirementsCalibrate the instrument accuracy within the measuring range by using standard solution or electrical method according to the product instructions. Rinse the container of the detector with water at least twice.

6.2 Blank Test: After rinsing the detector with water, measure the conductivity of the water and record it as γ₁. A blank test should be performed before each measurement. This step is not required when using a disposable detector.

6.3 Salt Extraction: Install the detector on the steel surface to be measured and operate according to the product instructions. Stir the water in the detector to extract surface salts.

6.4 Conductivity Measurement: Measure the conductivity of the water containing the extracted salts and record it as γ₂. The units are the same as for the blank test.

6.5 Detector Cleaning: After measurement, the detector should be emptied and thoroughly rinsed with water to obtain a conductivity of no more than 0.5mS/m.

Calculation and Presentation of Measurement Results

The total surface density of salts (ρₐ) is calculated using the following formula:

ρₐ = (C × V × Δγ) / A

Where: C is an empirical constant, taken as 5kg/(Ω·m²·S); V is the volume of the extraction water (m³); A is the surface area of the steel (m²); and Δγ is the rate of change in conductivity (S/m).

Results can be expressed in units such as "mg/m²" or "μg/cm²." Modern instruments are typically equipped with automatic calculation and unit conversion functions.

Implementation Recommendations and Precautions

Equipment Selection Recommendations: Select a conductivity meter that meets standard requirements, ensuring a measurement range of 0-20mS/m, an accuracy of ±3μS/cm, and a resolution better than 0.1mS/m. Calibration Management: Establish a comprehensive instrument calibration system. Calibration should be performed every 12 months by the manufacturer or a qualified laboratory according to the product manual, with calibration frequency increased if necessary. Personnel Training: Operators should receive professional training and become familiar with standard requirements, instrument operation methods, and data processing procedures to ensure the accuracy and reliability of measurement results. Quality Control: Establish complete quality control records, including instrument calibration records, blank test data, measurement results, and detector cleaning records. The implementation of GB/T 34430.4-2024 is of great significance to the shipbuilding industry: First, automated measurement methods significantly improve detection efficiency. Traditional methods require manual sampling and laboratory analysis, while automated methods can quickly complete measurements on-site. Second, standardized operations ensure the consistency and comparability of measurement results, providing a reliable technical basis for ship coating quality control.

Finally, this standard is aligned with international standards, helping to enhance the international competitiveness of my country's shipbuilding industry and promote advancement and innovation in ship coating technology.

Through the implementation of this standard, shipbuilding companies will be able to better meet PSPC requirements, improve coating quality, extend the service life of ships, reduce maintenance costs, and provide strong guarantees for the safe operation of ships.