ASTM G192 Standard Test Method for Determining the Crevice Repassivation Potential of Corrosion-Resistant Alloys Using a Potentiodynamic-Galvanostatic-Potentiostatic Technique

ASTM G192 Introduction

ASTM G192 has been made to give a uniform procedure to measure the crevice passivation potential of various alloys like stainless steels, nickel-based alloys, and titanium in aqueous solutions that are corrosive in nature. Passivation potential is a useful electrochemical parameter that shows whether an alloy is capable of preventing crevice corrosion after it has already occurred. The method is characterized by a controlled sequence of potential sweeps, galvanostatic holds, and potentiation monitoring to mimic service conditions. ERP can give engineers an idea of how vulnerable the material is to crevice corrosion and provide comparisons between materials on standardized laboratory tests.

ASTM G192 Test Method

ASTM G192 Equipment and Sample Preparation

ASTM G192 Results and Interpretation

The major outcome of this test is the crevice repassivation potential in volts with reference to an electrode like Ag/AgCl or saturated calomel. An increasing value of Erp means a higher tendency of the material to prevent crevice corrosion once it has occurred. The materials that exhibit values of Erp that are higher than conventional service potentials are less susceptible to progressive crevice attack. Data trends may be compared among alloys, among heat treatments, or among surface conditions to choose materials with better passivation behavior regarding the desired service conditions.

ASTM G192 Related Test Methods

ASTM G78 is used in crevice corrosion testing of nickel-based alloys, and ASTM G150 in pitting and crevice corrosion resistance under potentiostatic control.

ASTM G192 Applications in Industry 

This approach is commonly used in the marine industry, in the chemical processing industry, in the pulp and paper industry, and in power generation, where alloys need to be subjected to chloride-containing environments in crevice conditions. It helps with material qualification, alloy grade comparison, and the suitability of components like heat exchanger plates, fasteners, gaskets, and bolted joints where crevices may form.

ASTM G192 Materials Commonly Tested

The standard materials evaluated include austenitic and duplex stainless steels, high-performance nickel-based alloys, titanium and its alloys, and other corrosion-resistant metals (like nickel) in chloride-containing (or otherwise aggressive) aqueous environments.

ASTM G192 Common Challenges and Troubleshooting

Precision is best achieved in the control of solution chemistry, temperature, and crevice geometry. Non-optimal crevice seals, contamination of the specimen surface, or variations in electrochemical control may result in a non-reproducible result. The calibration of electrodes and clean reference electrodes is very important to the accuracy of potential. 

ASTM G192 Safety and Best Practices

Environmental and laboratory waste disposal regulations should be followed when disposing of solutions. Tests are expected to take place in an airy laboratory, equipped with adequate fume removal in case it is required.

Importance of ASTM G192 Test Method

This test method provides useful information on an alloy repassivation capacity after localized dissolution of the passive film. This aspect is critical in the long-term performance in service, by evaluating the repassivation potential of a crevice. Its results are mainly applied in the selection of materials, quality assurance, and life prediction of parts in industries like the marine industry, the chemical processing industry, the oil and gas industry, and the power generation industry.