DIN 50958 Electroplating - Modified Corrosion Test (Mod. CORR-Test)

The standard “DIN 50958 Electroplating - Modified corrosion test (mod. CORR-Test)”, published by the German Institute for Standardization (DIN), describes a corrosion resistance testing method. The procedure described in this standard serves as a corrosion resistance test, particularly for objects made of aluminum and steel with nickel-chromium or copper-nickel-chromium plating, zinc alloy cast objects with copper-nickel-chromium plating, and objects made of copper or copper materials with nickel-chromium plating.

The latest update to the DIN 50958 standard does not include the corrosion prevention procedure specified in the DIN EN ISO 4541 standard; instead, it incorporates a modified corrosion prevention procedure developed at that time based on the ASTM B380 standard. The modified corrosion prevention procedure differs from the procedure specified in the DIN EN ISO 4541 standard in the following key points:

• The DIN EN ISO 4541 standard specifies a temperature of 38 degrees plus/minus 1 degree and a relative humidity between 80 and 90 percent. In contrast, this standard specifies a temperature of 40 degrees plus/minus 3 degrees and a relative humidity of 100 percent. This climate is easier to maintain and corresponds to the conditions commonly applied in Germany.
• The requirement that the applied slurry be allowed to dry at a relative humidity lower than 50% is not adopted in this standard. Previous experience has shown that these deviations do not affect the test results of the modified corrosion inhibitor procedure.
• The thickness of the wet slurry should be approximately 50 µm. In contrast, the DIN EN ISO 4541 standard specifies a higher thickness of the wet slurry (between 80 µm and 200 µm).
• Unless otherwise specified, test specimens should be stored in a climate chamber for 16 hours, during which time the chamber should not be opened. In contrast, the DIN EN ISO 4541 standard specifies an exposure period of up to 16 hours during which the climate chamber should not be opened except for brief interruptions necessary for the insertion or removal of (other) test specimens.
• After testing, corrosion spots are made visible after exposure for 24 hours in a constant humidity condensation atmosphere according to DIN EN ISO 6270-2, or for 4 hours in a neutral salt spray test according to DIN EN ISO 9227. In contrast, DIN EN ISO 4541 specifies a 4-hour exposure time in a salt spray chamber according to ISO 3768, or an exposure time in a humidity chamber at 38 degrees Celsius and 100% relative humidity, to make corrosion spots visible.

The DIN 50958 standard includes a specific corrosion test method for electroplating coatings. This standard defines a procedure for evaluating the corrosion resistance of metallic coatings, especially multilayer electroplating systems. It is particularly applicable to the following cases:

• Steel surfaces coated with nickel-chromium or copper-nickel-chromium layers.
• Aluminum materials with protective coating.

This test simulates corrosive environmental conditions more aggressively than some traditional methods and is therefore useful in evaluating decorative and functional coatings in the automotive, plumbing, hardware, and other industries where parts are exposed to road salt, moisture, and atmospheric pollutants.

It is commonly applied to decorative chrome-plated components (e.g., car upholstery, faucets, household items) to control pitting, rusting, or coating deterioration.

This method is a modified version of the classic CORR-Test originally defined in the ASTM B380 standard. The “Mod. CORR-Test” standard adapts and improves the procedure for better repeatability and suitability to industrial needs.

The testing process generally follows these steps:

• Preparation of CORR-Test paste: A special abrasive paste/mixture is prepared and includes: kaolin (or a similar inert carrier), copper(II) chloride, iron(III) chloride and nitric acid or other activators.
• Application: The paste is applied or spread evenly onto the test sample (coated part) to a defined thickness using a brush.
• Exposure: The coated sample is placed in a humidity chamber (typically at a high temperature and near 100% relative humidity) for a specific period of time. This promotes electrochemical corrosion reactions in defects or pores in the coating.
• Duration: Test durations vary depending on the required level of severity (typically 20-200 hours, sometimes longer), with multiple screening intervals.
• Assessment: Following exposure, the sample is cleaned and examined for the following aspects:
• Corrosion spots / pitting
• Rust formation (on steel surfaces)
• Blistering, peeling, or loss of adhesion
• Rating is usually done visually, sometimes with the help of rating scales or comparison samples.

The test is considered quite demanding and correlates very well with real-world performance in chloride-rich environments (e.g., winter road conditions).

Compared to other corrosion tests,

• Salt spray (DIN EN ISO 9227 standard): Continuous salt mist.
• Condensation / moisture (DIN EN ISO 6270-2 standard): Pure moisture without salt.
• Cyclic corrosion tests (VDA 233-102 and GMW 14872 standards): Alternating dry/wet/salt.

DIN 50958 (mod. CORR-Test) is more specific for decorative multi-layer nickel/chrome plating and uses paste application instead of misting or dipping.

Today, this standard continues to be used as a reference in the following areas:

• Automotive supplier specifications
• Test laboratories for galvanic coatings.
• Quality control of electroplated parts.

Although some international specifications have shifted towards cyclical testing (e.g., VDA, SAE), the modified CORR-Test method is still widely used in Europe for specific product qualifications.

In conclusion, the DIN 50958 standard is a corrosion testing standard that historically provides laboratory procedures for evaluating the corrosion resistance of metallic materials and coatings. This test method continues to be an important reference in quality systems.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services in accordance with the DIN 50958 standard.