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ASTM B368 Standard Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)

ASTM B368, with its Copper-Accelerated Acetic Acid-Salt Spray (CASS) test method, is a fundamental and widely accepted standard for assessing the corrosion resistance of various materials. By understanding the significance of salt spray test hours, test standards, and equipment, businesses can make informed decisions about implementing effective corrosion testing protocols. Incorporating the ASTM B368 test into their quality inspection processes will help organizations ensure the durability and reliability of their products, leading to increased customer trust and satisfaction.

The ASTM B368 standard test method provides a thorough and reliable framework for conducting accelerated corrosion testing, specifically in the form of a salt spray or fog test. It aims to simulate and assess the potential damage caused by accelerated corrosion processes on metallic surfaces, assemblies, and coatings. When it comes to testing the durability and corrosion resistance of various materials and coatings, The ASTM B368 standard test method, commonly known as the Copper-Accelerated Acetic Acid-Salt Spray (CASS) test, is widely recognized and employed.

One crucial aspect of the CASS test is the duration for which the test specimens are exposed. To execute the ASTM B368 test accurately, a controlled testing environment is essential. This section will provide insights into salt spray test chambers and cabinets, explaining their role in creating the corrosive atmosphere required for the test. It will highlight crucial considerations when choosing a suitable test chamber and emphasize the importance of adhering to proper maintenance protocols for reliable and consistent results.

ASTM B368 Standard Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)

The Cyclic Accelerated Salt Spray (CASS) test is a widely employed and highly valuable method for various applications in the electroplating industry. Its versatility makes it an essential tool for specification acceptance, simulated service evaluation, manufacturing control, and research and development processes. Originally designed for decorative, electrodeposited nickel/chromium and copper, nickel, chromium coatings, the CASS test has revolutionized the electroplating industry.

By subjecting electroplated parts to rigorous salt spray conditions, it has significantly improved the quality of these parts, leading to the development of new and superior electroplating processes. The significance of the CASS test lies in its ability to provide accurate and reliable results that reflect real-world performance. By mimicking harsh environmental conditions, such as salt spray exposure, the test helps evaluate the durability, corrosion resistance, and overall quality of electroplated coatings. This information is vital for manufacturers and researchers to ensure compliance with industry standards, enhance product performance, and meet customer expectations.

Mode and Description WEW-YW-60D WEW-YW-90D WEW-YW-110D
Inner Dimension(mm) 600*450*400 900*600*500 1000*750*500
Outer Dimension(mm) 1070*600*1180 1410*880*1280 1600*1050*1200
Test Room Size (Liters) 108 Liters 270 Liters 420 Liters
Power Supply AC 220V, 50Hz AC 220V, 50Hz AC 220V, 50Hz
Power Current 1Phase, 1.5 kW 1Phase, 2.0 kW 1Phase, 2.5 kW
Lid Opening Method Manual Opening Manual Opening Manual Opening
Brine Tank Volume 15 Literes 25 Literes 30 Literes
Test Room Temp Range Ambient Temperature +5℃ – +30℃, Ventilation is recommended, if the temperature exceeds +30℃, it is recommended to adjust the room temperature by suitable means. Ambient humidity should be controlled below 80%RH.
Test Room Temp Range RT+10℃ – +55℃ RT+10℃ – +55℃ RT+10℃ – +55℃
Saturated Barrel  RT+10℃ – +70℃ (Purpose: Heating and filtering of compressed air to reduce nozzle crystallisation.)
Temp Performance Temperature Uniformity: ≤2℃,  Temperature Fluctuation: ≤ ±0.5°C Temperature Uniformity: ≤2℃, 
Salt Mist Settling Rate 1~2 ml/80 cm2/h (Take 16 Hours To Test The Average Value)|1~2 ml/80 cm2/h
Spray Method Continuous, Intermittent,  Programmable Tests Continuous, Intermittent, 
Testing Type NSS, AASS NSS, AASS,CASS NSS, CASS
Safety Devices Low Water Level Alarm|Over-Temperature Alarm (Mechanical Over-Temperature Protection + Electronic Over-Temperature Protection Double Over-Temperature Protection)
Air Requirements Inlet Pressure Above 0.4Mp. Two-Stage Pressure Regulation. Spray Pressure 0.07~0.17mp (Adjustable)
Sample Holder One Set Each Of V-Groove And O-Round Bar (Combined To Form An Angle Of 20°±5%).
Standard Configuration 1 Set Of V-Type/O-Type Shelves, 2 Bottles Of Test Drug Sodium Chloride (500g/Bottle), 1 Plastic Anti-Rust Bucket (5l Capacity), 1 Nozzle
salt spray testing
4.1 The apparatus required for the CASS test consists of a fog chamber, a salt-solution reservoir, a supply of compressed air, one or more atomizing nozzles, specimen supports, provision for heating the chamber, and necessary means of control. 4. Apparatus
4.2 The size and detailed construction of the apparatus are optional, provided the conditions meet the requirements of this test method. The construction of the apparatus is described in the appendix of Test Method B117. For the CASS test, however, the requirements for air pressure and temperature are typically 0.08 to 0.12 MPa and 60 to 65°C, respectively. The actual air pressure will be that required to produce the proper collection rate (see 8.3.1).
4.3 The apparatus shall be constructed so that drops of solution that accumulate on the ceiling or cover of the chamber do not fall on the specimens being tested. Drops of solution that fall from the specimens shall not be returned to the solution reservoir for respraying.
4.4 Materials of construction shall not affect the corrosiveness of the fog, nor be themselves corroded by the fog.
5.1 Prepare the salt solution by dissolving 5 parts by weight of salt in 95 parts of water conforming to Specification D1193, Type IV. The salt shall be sodium chloride (NaCl), ACS reagent grade, or equivalent. The pH of this solution shall be between 6.0 and 7.0. Impurities or contamination ofeither the salt or the water, or both, shall be suspected if the pH is outside of this range (Note 2). No adjustment should be made. 5. Test Solution
5.2 Add 0.25 g of reagent grade copper chloride (CuCl 2 ·2H 2 O) to each liter of the salt solution; dissolve and mix thoroughly.
5.3 The pH of the salt-copper solution shall be adjusted to the range of 3.1 to 3.3, as measured on a sample of the collected spray, by the addition of glacial acetic acid, ACS reagent grade, or equivalent (Note 3). The pH measurement shall be made electrometrically at 25°C. Before the solution is atomized, it shall be free of suspended solids (Note 4).
Note 2: Reference Practice B117 and Test Method E70 for requirements on salt. The made up CASS solution should be adjusted to a specific gravity of 1.030 to 1.040, when measured at a temperature of 25°C, will meet the concentration requirement. It is suggested that a daily check be made.
Note 3: The initial solution may be adjusted to a pH that gives the proper pH range in the collected solution. Adjustment of the initial pH for makeup solution is based upon the requirements to maintain the required pH of the collected samples. If less than 1.3 or more than 1.6 mL of the glacial acetic acid are required per litre of sodium chloride and copper solution to attain the specified pH, some discrepancy in the system may be suspected (the purity of the water or salt, or both; the accuracy of the pH meter; the general cleanliness of the system; etc.).
Note 4: The freshly prepared salt solution may be filtered or decanted before it is placed in the reservoir, or the end of the tube leading from the solution to the atomizer may be covered with a double layer of cheese cloth to prevent plugging of the nozzle.
6.1 The compressed air supply to the nozzle or nozzles for atomizing the test solution shall be free ofoil and dirt (Note 5). 6. Air Supply
Pressure shall be adequate to provide a specified condensate rate.
Note 5: The air supply can be freed of oil and dirt by passing it through a water scrubber or at least 60 cm of suitable cleaning material, such as sheep’s wool, excelsior, slag wool, or activated alumina. Commercial filters for compressed air may be used.
Note 6: Atomizing nozzles may have a critical pressure, at which an abnormal increase in the corrosiveness ofthe salt fog occurs. Ifthe critical pressure of a nozzle has not been determined with certainty, control of fluctuation in the air pressure within 60.0007 MPa by installing a pressure regulator valve minimizes the possibility that the nozzle will be operated at its critical pressure. Pressure of 0.10 6 0.02 MPa has been found satisfactory.

Moreover, the CASS test has played a crucial role in driving innovation within the electroplating industry. Through its application, manufacturers have been able to identify and address shortcomings in existing processes, leading to the development of new and advanced electroplating techniques. These advancements have not only improved the overall quality of electroplated parts but have also allowed for the creation of coatings with enhanced properties, such as increased corrosion resistance, durability, and aesthetic appeal.

In addition to its technical significance, the CASS test also holds substantial commercial value. By employing this standardized testing method, manufacturers can confidently demonstrate the quality and reliability of their electroplated products to potential customers. This, in turn, instills trust and confidence in buyers, leading to increased business opportunities and market share.

The CASS test stands as a pivotal tool in the electroplating industry. Its widespread use across various stages, from specification acceptance to research and development, highlights its significance and impact. Through its implementation, the quality of electroplated parts has been elevated, and new and superior electroplating processes have been developed. The CASS test not only helps ensure compliance with industry standards but also drives innovation and improves the overall customer experience. Its combination of technical and commercial value solidifies its position as a vital component in the advancement of the electroplating industry.

salt spray fog apparatus
7.1 The type and number of test specimens to be used, as well as the criteria for the evaluation ofthe test results, shall be defined in the specifications covering the material or product being tested or shall be mutually agreed upon between the purchaser and the supplier. 7. Test Specimens
8.1 Preparation of Test Specimens:  Clean metallic and metallic coated specimens. Unless otherwise agreed upon, clean decorative copper/nickel/chromium or nickel/chromium coatings immediately before testing by wiping significant surfaces with a cotton pad saturated with a slurry containing 10 g ofpure magnesium oxide powder (ACS reagent grade) in 100 mL of distilled water.  8. Procedure
Upon rinsing in warm running water, be sure that the clean surface is free of water break. Anodized aluminum parts may be cleaned with inhibited 1,1,1- trichloroethane or other suitable organic solvent (see Warning). Do not clean organic and other nonmetallic coated specimens. Other methods of cleaning, such as the use of a nitric-acid solution for the chemical cleaning or passivation of stainless steel specimens, are permissible when agreed upon between the purchaser and the supplier. 
Take care that the specimens after cleaning are not recontaminated by excessive or careless handling. Protect the cut edges of plated, coated, or multilay-ered materials and areas containing identification marks or in contact with the racks or supports with a coating that is stable under the conditions of the test, such as wax, stop-off lacquer, or pressure-sensitive tape. (Warning: 1,1,1-Trichloroethane should be used in a well-ventilated area away from open flames.)
8.2 Positioning ofSpecimens: Position the specimens in the CASS test chamber during the test so that the following conditions are met:
8.2.1 Support or suspend the specimens 15 – 30° from the vertical and preferably parallel to the principal direction of horizontal flow of fog through the chamber, based upon the dominant surface being tested, avoiding pooling of solution on the sample. See Note 8 on automobile parts.
8.2.2 The top of the specimen shall not be higher than the top of the collection tubes.
8.2.3 Make sure the specimens do not come in contact with each other or any other metallic material or any material capable of acting as a wick.
8.2.4 Place each specimen so as to permit free settling offog on all specimens.
8.2.5 Make sure the salt solution from one specimen does not drip on any other specimen.
8.2.6 Place the specimens in the chamber just prior to bringing the test chamber to the required temperature and turning on the air, since storage in an idle chamber overnight, or for other significant length of time, can affect test results.
Note 7: Suitable materials for the construction or coating of racks and supports are glass, rubber, plastic, or suitably coated wood. Bare metal should not be used. Specimens are preferably supported from the bottom or the side. Slotted wooden strips are suitable for the support offlat panels. Suspension from glass hooks or waxed string may be used as long as the specified position of the specimens is obtained. If necessary, such suspension may be made by means of secondary support at the bottom of the specimens.
Note 8: Support suspend automobile parts, however, so as to expose all significant surfaces at the general level of the condensate collectors. If B368 − 09 (2014) 2 the position on the automobile is vertical, place the part in an incline position 15-30° from vertical to allow surface wetting by the condensate. If the position on the automobile is facing down, rotate the part approximately 180° to test the significant surface. If there are several significant surfaces at different angles, expose each surface ofone or more specimens.
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8.3 Conditions in the Salt-Spray Chamber: Maintain the exposure zone of the CASS test chamber at a temperature of 496 1°C during the exposure period (Note 9).The test duration shall commence when the temperature is 49 6 1°C and fog is present in the chamber. Heat the air supply by passing fine bubbles through heated distilled or deionized water (see Specification D1193, Type IV) so that the temperature of the air after expansion at the nozzle is 49 6 1°C. Record the temperature within the exposure zone of the closed cabinet (Note 10) twice a day at least 7 h apart (except Saturdays, Sundays, and holidays, when the salt-spray test is not inter- rupted for exposing, rearranging, or removing test specimens or to check and replenish the solution in the reservoir).
Note 9: This can be best accomplished by preheating the chamber to 49°C before starting solution atomization.
Note 10: A suitable method to record the temperature is by a thermometer that can be read from outside the closed cabinet. The recorded temperature must be obtained with the salt-spray chamber closed to avoid a false low reading, because ofwet-bulb effect when the chamber is open. Automatic control oftemperature in the chamber and a continuous record of temperature are desirable.
8.3.1 Place at least two or more (depending on the size of the cabinet) clean fog collectors within the exposure zone so that no drops of solution will be collected from the test specimens or any other source. Position the collectors in each corner. The arrangement is shown in Fig. 1. Make sure that the fog is such that for each 80 cm 2 of horizontal collecting area each collector collects from 1.0 to 2.0 mL/h of solution, based on a typical run of at least 22 h (Note 11). Maintain the sodium chloride concentration of the collected solution between 4.5 and 5.5 mass % (Note 12 and Note 13). Dilution and evaporation of condensate should be avoided (Note 14).
Note 11: Suitable collecting devices are glass funnels with the stems inserted through stoppers into graduated cylinders. Funnels with adiameter of 10 cm (area of about 80 cm 2 ) and 50-mL cylinders are preferred.
Note 12: A solution having a specific gravity of from 1.030 to 1.040, when measured at 25°C, will meet the concentration requirement. The concentration may also be determined as follows: Dilute 5 mL of the collected solution to 100 mL with distilled water and mix thoroughly; pipet a 10-mL aliquot into an evaporating dish or casserole; add 40 mL of distilled water and 1 mL of 1% potassium chromate (K 2 CrO 4 ) (ACS reagent grade with less than 0.005% chloride) and titrate with 0.1 Nsilver nitrate (AgNO 3 ) (ACS reagent grade) solution to the first appearance of a persistent red coloration. A test solution that requires between 3.9 and 4.9 mL of 0.1 N Ag NO 3 solution will meet the concentration requirements.
FIG 1 Arrangement of Fog Collectors
Note 13: It has not been found necessary to check copper concentration of the collected solution.
Note 14: Factors that may contribute to dilution and evaporation of condensate and make it difficult to control the concentration are lower temperature, inadequate cover insulation, and prolonged storage of test solution at above room temperature.
8.3.2 Direct or baffle the nozzle or nozzles so that none of the spray can impinge directly on the test specimens.
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8.4 Continuity of Test: Unless otherwise specified in the specification covering the material or product being tested, the test shall be continuous for the duration of the entire test period. Continuous operation implies that the chamber be closed and the spray operating continuously, except for the short daily interruptions necessary to inspect, rearrange, or remove test specimens, to check and replenish the solution in the reservoir, and to make necessary recordings as described in 8.3. Schedule operations so that these interruptions are held to a minimum.
8.5 Period of Test: Designate the period of test by the specifications covering the material or product being tested or as mutually agreed upon between the purchaser and the supplier.
Note 15: Typical exposure periods are: 6, 16, 22, 44, 110, 192, 240, 504, and 720 h. Parts may be rinsed prior to daily inspection.
8.6 Cleaning Tested Specimens: Unless specified in the specifications covering the material or product being tested, carefully remove specimens at the end of the test, rinse gently in clean, running, warm water (38°C, max) to remove salt deposits from their surfaces, and then dry. To dry the specimens use a stream ofclean, compressed air at 0.25 to 0.30 MPa max-gage pressure or air dry.
Note 16: If steel parts are rinsed immediately after removal from the test chamber, small rust spots or flakes of rust may lift off and be rinsed away. It is then difficult to tell where the spots had been. If, after removal from the test chamber, the part is allowed to dry 30 to 60 min before rinsing, all corrosion spots are easily visible. This not does not apply to zinc-die castings.
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8.7 Calibration of Corrosive Conditions: This procedure for calibration and standardization of the corrosive conditions within the cabinet involves exposure of nickel test panels and determination of their mass loss in a specified period of time. This may be done monthly or more frequently to make sure the cabinet is operating within the limits specified in 8.7.4. When performing benchmarking, co-relation studies or round robins nickel coupons shall be run and all data recorded.
8.7.1 Use nickel panels that are 7.5 by 10 cm, approximately 0.09 cm thick, and 77.5 cm ² (main face and 3 edges) and made from the higher carbon grade (0.15% max) given in Specifi- cation B162.
8.7.2 Place one weighed nickel test panel in each corner of the cabinet with the 10-cm length inclined 30° to the vertical using plastic supports that are about 1.5 by 4 by 7.5 cm. The four test panels should be on the inboard side ofthe condensate collectors parallel to the cabinet length. Make sure the top of the panels are at the same level as the top of the condensate collectors. See Note 17.
8.7.3 Expose the test panels to 22 h of CASS testing, recording test operating conditions on the data sheet as usual. FIG. 1 Arrangement of Fog Collectors B368 − 09 (2014)
Remove the panels from the cabinet and rinse each in reagent grade water (see Specification D1193, Type IV) to remove salt. Immerse each panel in 20% by volume hydrochloric acid prepared with distilled water for 2 min at 20 to 25°C using nickel-copper alloy 400 (UNS N04400) tongs. The tongs may be nonmetallic or another material that will not affect the mass loss of the nickel by galvanic action. Rinse each panel in water at room temperature and then in warm (38°C) flowing water. Dry panels in an oven at 100°C for 10 min. Allow the panels to reach room temperature and weigh immediately on an analytical balance.
8.7.4 Determine the mass loss of each panel by subtracting its weight after exposure from its initial weight. Determine the corrosive loss by dividing the mass loss by the area 77.5 cm ² (main face and 3 edges). The corrosive rate shall be 0.45 to 0.85 mg/cm 2 to satisfy the requirements of this test method.
Note 17: Condition the Panels – New panels may require “conditioning.” This can be achieved by pickling panels per 8.7.3 and then exposing them to CASS until proper weight loss is achieved. (may take 2-4 days) “Inactive Panels” – if panels are allowed to sit for a long period of time they may become passive and therefore will not produce the proper weight loss. They should be treated as if new, pickled and then exposed to CASS again until proper weight loss is achieved. Storing or running panels in the cabinet whenever the CASS cabinet is run is desirable to keep them in good condition.
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