MIL STD 810H Test Method 509.7 – Salt Fog Test Equipment

MIL STD 810H 509.7 salt spray test standard is a clear and specific stipulation for the salt spray test conditions, such as temperature, humidity, sodium chloride solution concentration and pH value, etc., and also puts forward technical requirements for the performance of the salt spray test chamber. The methods for judging the results of the salt spray test include: rating judging method, weighing judging method, corrosive appearance judging method, and corrosion data statistical analysis method. The products that need salt spray test are mainly some metal products, and the corrosion resistance of the products is investigated through testing.

The purpose of MIL STD 810H test method 509.7 is to evaluate the effectiveness and quality of the protective coating and surface treatment of military products and samples of the same material in a short time, and to find out the source of potential problems, defects in quality control and design Disadvantages and so on. Generally speaking, This method is only suitable for military products that are regularly (as opposed to rare or irregular) exposed to high-salt atmospheres|MIL-STD-810G Method 509.6 Salt Fog

MIL STD 810H Test Method 509.7 – Salt Fog Test Equipment
The salt fog Method is performed to determine the effectiveness of protective coatings and finishes on materials.  It may also be applied to determine the effects of salt deposits on the physical and electrical aspects of materiel. 1.1 Purpose 1. SCOPE
Use this Method for screening purposes only to evaluate the effectiveness and quality of protective coatings and finishes on materiel and material coupons, and to locate potential problem areas, quality control deficiencies, design flaws, etc., in a relatively short period of time.   1.2  Application
Although not representative of the natural environment (see paragraph 1.3b), this test has been used to provide an indication of potential problem areas associated with the salt (marine) environment.  
In general, Only apply this Method to materiel that will experience significant exposure (as opposed to infrequent or irregular) to high levels of salt in the atmosphere. 
Use of this mMethod to evaluate material coupons is not intended to be conducted in lieu of full assemblage testing.
This method does not attempt to duplicate the complex environment but, rather, it provides a generally stressful situation that may reveal potential problem areas in  materiel|GJB 150.11A Laboratory Environmental Test Methods For Military Materiel Part 11 : Salt Fog Test 1.3  Limitations
Testing in the  natural environment, whenever practical, may provide more valuable results. Specifically, this Method does not address:
a.There is no relationship between this test and any real world exposure duration.  The test is not intended to duplicate the effects of a marine atmosphere due to variations in chemical composition and concentrations of the various marine and other corrosive environments.
b.It has not been demonstrated that a direct relationship exists between salt fog corrosion and corrosion due to other media.
c.It has not been demonstrated that withstanding the effects of this test guarantees materiel will survive under all corrosive conditions.  For acidic atmosphere tests, see Method 518.2.  Consult ASTM G85, “Standard Practice for Modified Salt Spray (Fog) Testing” (paragraph 6.1, reference a) for information on introducing a sulfur dioxide environment.    
c. Caution: Introducing  sulfur  dioxide  in  the  salt  fog  chamber  may contaminate the chamber for future salt fog tests.
d.This test has proven to be generally unreliable for predicting the service life of different materials or coatings.
e.This test is not a substitute for evaluating corrosion caused by humidity and fungus because their effects differ from salt fog effects and the tests are not interchangeable.
After examining requirements documents and applying the tailoring process in Part One of this standard to determine where atmospheric corrosion is anticipated in the life cycle of materiel, use the following to confirm the need for this Method and to place it in sequence with other methods. 2.1 Selecting the Salt Fog Method 2. TAILORING GUIDANCE
Salt is one of the most pervasive chemical compounds in the world. It is found in the oceans and seas, the atmosphere, ground surfaces, and lakes and rivers. It is impossible to avoid exposure to salt. The worst effects occur, in general, in coastal regions.    2.1.1 Effects of Corrosive Environments
The effects of exposure of materiel to an environment where there is a corrosive atmosphere can be divided into three broad categories:  corrosion effects, electrical effects, and physical effects. 
Consider the following typical problems to help determine if this method is appropriate for the material being tested. This list is not intended to be all-inclusive. 
a. Corrosion due to electrochemical reaction.
b. Accelerated stress corrosion.
c. Formation of acidic/alkaline solutions following salt ionization in water. Corrosion Effects
a. Impairment of electrical materiel due to salt deposits.
b. Production of conductive coatings.
c. Corrosion of insulating materials and metals. Electrical Effects
a. Clogging or binding of moving parts of mechanical components and assemblies.
b. Blistering of paint as a result of electrolysis.
a. General. Use the anticipated life cycle sequence of events as a general sequence guide (see Part One, paragraph 5.5). 2.1.2 Effects of Corrosive Environments
b. Unique to this Method. If the same test item is to be used for additional testing, it is imperative that the test item be thoroughly cleaned following the Salt Fog test.  Salt deposits can interfere with the effects of other tests.  
In most cases recommend the salt fog test be conducted after the other climatic tests.  It is generally inappropriate to conduct the salt fog, fungus and humidity tests on the same test sample because the cumulative of effects from the three environments may be unrealistic.  
However, if it is necessary to do so, perform the salt fog test following the fungus and humidity tests.  Although generally inappropriate, if sand and dust testing is required on the same test item, perform it following salt fog testing.   Recommend conducting the sequence of testing in accordance with the LCEP.
This Method has one procedure. Possible variations are described below. 2.2  Selecting Procedure Variations
Unless otherwise identified, use a 5 ± 1 percent salt solution concentration (paragraph 6.1, reference b.) 2.2.1 Salt Solution
Use water as described in Part One, paragraph 5.16.  
The intent is to not introduce contaminants or acidic/alkaline conditions that may affect the test results. (See paragraph
The configuration and orientation of the test item during the exposure period of the salt fog test is an important factor in determining the effect of the environment on the test item.   2.2.2 Test Item Configuration
Unless otherwise specified, configure the test item and orient it as would be expected during its storage, shipment, or use.  
The listing below offers the most likely configurations that materiel would assume when exposed to a corrosive atmosphere.  For test purposes, choose the most severe/critical configuration.
a. In a shipping/storage container or transit case.
b. Outside of its shipping/storage container but provided with an effective environmental control system that partly excludes the salt fog environment.
c. Outside of its shipping/storage container and set up in its normal operating mode.
d. Modified with kits for special applications or to compensate for mating components that are normally present, but are not used for this specific test.
Experience has shown that alternating 24-hour periods of salt fog exposure and drying conditions for a minimum of four 24-hour periods (two wet and two dry), provides more realistic exposure and a higher damage potential than does continuous exposure to a salt atmosphere (paragraph 6.1, reference b).   2.2.3 Duration
If this option is not acceptable (e.g., security issues, LCEP information, or commodity requirements), perform 48 hours of exposure followed by 48 hours of drying.   
Increase the number of cycles to provide a higher degree of confidence in the ability of the materials involved to withstand a corrosive environment. 
Maintain the temperature in the chamber at 35 ±2 °C (95 ±3.6 °F).  This temperature has been historically accepted and is not intended to simulate actual exposure situations. Other temperatures may be used if appropriate. 2.2.4 Temperature
Ensure the air velocity in test chambers is minimal (essentially zero). 2.2.5 Air Circulation
Adjust the salt fog fallout such that each receptacle collects from 1 to 3 ml of solution per hour for each 80 cm2 of horizontal collecting area (10 cm (3.94 in.) diameter). 2.2.6 Fallout Rate
If corrosion levels from test to test are to be compared, and accepting that the rate of corrosion is much higher during the transition from wet to dry, it is critical to closely control the rate of drying. 2.2.7 Dryout Rate
MIL STD 810H Test Method 509.7 – Salt Fog Test Equipment

Salt Fog Testing and MIL-STD-810G Salt Spray Apparatus: Salt fog testing is performed to assess the ability of equipment and materials to withstand exposure to salt-laden environments. The MIL-STD-810G standard specifies the test conditions and procedures to evaluate the performance of equipment in such environments. Manufacturers often rely on MIL-STD-810G salt spray apparatus, designed specifically for the salt fog test method, to ensure their products can endure challenging operating conditions.

The MIL STD 810G salt fog test involves subjecting test samples to a corrosive salt fog atmosphere to evaluate their resistance to corrosion and functional degradation. This test method helps manufacturers assess the effectiveness of protective coatings, seals, and enclosures against salt-induced corrosion. By simulating real-world conditions, the salt fog test aids in designing and producing reliable products capable of withstanding aggressive environmental elements.

To comply with MIL-STD-810G salt fog test requirement, Wewon Environmental Chambers Co., Ltd. require specifically designed salt spray test apparatus. These apparatus are built to deliver accurate and standardized salt fog conditions to ensure consistent and repeatable test results. Advanced salt spray test apparatus offer features like precise temperature and humidity control, adjustable spray density, uniform distribution, and automatic data logging. These features enable Wewon Tech to perform comprehensive and precise salt fog tests on their products.

The following information is required to conduct salt fog tests adequately. 3.1 Pretest 3. INFORMATION REQUIRED
a. General. Information listed in Part One, paragraphs 5.7 and 5.9, and Annex A, Task 405 of this standard. 
(1) Areas of the test item visually and functionally examined and an explanation of their inclusion or exclusion. b. Specific to this Method
(2) Salt concentration if other than 5 percent. 
(3) Resistivity and type of initial water.
(4) The appropriate exposure option, i.e., 24/24/24/24-hrs, or 48/48-hrs (see paragraph 2.2.3).
c. Tailoring. Necessary variations in the basic test procedures to accommodate environments identified in the LCEP.
Collect the following information during conduct of the test: 3.2 During Test
a. General. Information listed in Part One, paragraph 5.10, and in Annex A, Tasks 405 and 406 of this standard.
(1) Record of chamber temperature versus time conditions. b. Specific to this Method
(2) Salt fog fallout quantities per unit of time (paragraph 4.1.4). 
(3) Salt fog pH (paragraph
The following post test data shall be included in the test report. 3.3 Post-Test
a. General. Information listed in Part One, paragraph 5.13, and in Annex A, Task 406 of this standard. 
(1) Areas of the test item visually and functionally examined and an explanation of their inclusion or exclusion. b. Specific to this Method
(2) Test variables:
(a) Salt solution pH.
(b) Salt solution fallout rate (ml/cm2/hr).
(3) Results of examination for corrosion, electrical, and physical effects. 
(4) Observations to aid in failure analysis (to include photographs).
(5) Any deviation from the approved test plan.
Ensure the apparatus used in performing the salt fog test includes the following.     4.1 Test Facility 4. TEST PROCESS
Use supporting racks that do not affect the characteristics of the salt fog mist.   4.1.1 Test Chamber
No part of the test setup that contacts the test item may induce electrolytic corrosion.  
Do not allow condensation to drip on the test item.  
Do not return any liquid that comes in contact with either the chamber or the test item to the salt solution reservoir.  
Vent the exposure area to prevent pressure buildup.  
Ensure the test chamber has a waste collection system so that all waste material can be analyzed prior to disposal. 
Dispose of any material determined to be hazardous waste in accordance with local, state and federal regulations.
Ensure the salt solution reservoir is made of material that is non-reactive with the salt solution, e.g., glass, hard rubber, or plastic. 4.1.2 Salt Solution Reservoir
Filter the salt solution (Figures 509.6-1 and -2) and inject it into the test chamber with atomizers that produce a finely divided, wet, dense fog.   4.1.3 Salt Solution Injection System
Use atomizing nozzles and a piping system made of material that is non-reactive to the salt solution.  
Do not let salt buildup clog the nozzles. Suitable atomization has been obtained in chambers having a volume of less than 0.34 m3 (12 ft3) under the following conditions:
a. Nozzle pressure as low as practical to produce fog at the required rate. 
b. Orifices between 0.5 and 0.76 mm (0.02 and 0.03 in.) in diameter.
c. Atomization of approximately 2.8 liters of salt solution per 0.28 m3  (10 ft3) of chamber volume per 24 hours.
When chambers with a volume considerably in excess of 0.34 m3 (12 ft3) are used, the conditions specified may require modification.
Figure 509.6-1. Location of Salt Solution Filter
Figure 509.6-1. Location of salt solution filter
Figure 509.6-2. Salt Solution Filter
Figure 509.6-2. Salt solution filter
Use a minimum of two salt fog collection receptacles to collect water solution samples.  Locate one at the perimeter of the test item nearest to the nozzle, and the other also at the perimeter of the test item but at the farthest point from the nozzle.   4.1.4 Salt Fog Collection Receptacles
If using multiple nozzles, the same principles apply. Position the receptacles such that they are not shielded by the test item and will not collect drops of solution from the test item or other sources.  
Preheat the oil-free and dirt-free compressed air used to produce the atomized solution (to offset the cooling effects of expansion to atmospheric pressure) (see Table 509.6-I). 4.2 Controls
Table 509.6-I. Air Pressure and Preheat Temperature Requirements for Operation at 35 °C (95 °F)
Table 509.6-I. Air pressure and preheat temperature requirements for operation at 35 °C (95 °F)
Test interruptions can result from two or more situations, one being from failure or malfunction of test chambers or associated test laboratory equipment.  4.3 Test Interruption
The second type of test interruption results from failure or malfunction of the test item itself during required or optional performance checks.
a. General. See Part One, paragraph 5.11 of this standard.  4.3.1 Interruption Due to Chamber Malfunction
(1) Undertest interruption. If an unscheduled test interruption occurs that causes the test conditions to exceed allowable tolerances toward standard ambient conditions, give the test item a complete visual examination and develop a technical evaluation of the impact of the interruption on the test results.  b. Specific to this Method
Restart the test at the point of interruption and restabilize the test item at the test conditions.
(2) Overtest interruption. If an unscheduled test interruption occurs that causes the test conditions to exceed allowable tolerances away from standard ambient conditions, stabilize the test conditions to within tolerances and hold them at that level until a  complete visual examination and technical evaluation can be made to determine the impact of the interruption on test results. 
If the visual examination or technical evaluation results in a conclusion that the test interruption did not adversely affect the final test results, or if the effects of the interruption can be nullified with confidence, restabilize the pre-interruption conditions and continue the test from the point where the test tolerances were exceeded.
Failure of the test item(s) to function as required during mandatory or optional performance checks during testing presents a situation with several possible options. 4.3.2 Interruption Due to Test Item Operation Failure
a. The preferable option is to replace the test item with a “new” one and restart from Step 1.
b. A second option is to replace / repair the failed or non-functioning component or assembly with one that functions as intended, and restart the entire test from Step 1.
Note: When evaluating failure interruptions, consider prior testing on the same test item and consequences of such.
a. General. See Part One, paragraph 5.8. 4.4 Test Setup
b. Unique to this Method. Ensure the fallout collection containers are situated in the chamber such that they will not collect fluids dripping from the test item.
The following steps, alone or in combination, provide the basis for collecting necessary information concerning the test item in a salt fog environment. 4.5 Test Execution
Before starting the  test, determine the test details (e.g.,  procedure variations, test  item configuration, cycles, durations, parameter levels for storage/operation, etc.) from the test plan. (See paragraph 3.1 above.) Preliminary Steps 4.5.1 Preparation for Test
(1)  Handle the test item as little as possible. Prepare the test item for testing immediately before exposure. a. Handling and configuration
Unless otherwise specified, ensure the test item surfaces are free of surface contamination such as oil, grease, or dirt that could cause a water break.  
Do not use corrosive solvents, solvents that deposit either corrosive or protective films, or abrasives other than a paste of pure magnesium oxide in any cleaning methods.
(2) Configure the test item as specified in the test plan and insert it into the test chamber.
For this test, use sodium chloride containing (on a dry basis) not more than 0.1 percent sodium iodide and not  more than 0.5 percent total impurities.    b. Preparation of salt solution
Do not use sodium chloride containing anti-caking agents because such agents may act as corrosion inhibitors.   
Unless otherwise specified, prepare a 5 ±1 percent solution by dissolving 5 parts by weight of salt in 95 parts by weight of water.  Adjust to and maintain the solution at a specific gravity (Figure 509.6-3 and Table 509.6-II) by using the measured temperature and density of the salt solution.   
If necessary, add sodium tetraborate (borax) to the salt solution as a pH stabilization agent in a ratio not to exceed 0.7g sodium tetraborate to 75 liters of salt solution.   
Maintain the pH of the salt solution, as collected as fallout in the exposure chamber, between 6.5 and 7.2 with the solution temperature at +35 ±2 °C (95 ±4 °F).  
To adjust the pH, use only diluted chemically pure hydrochloric acid or chemically pure sodium hydroxide.   
Make the pH measurement either electrometrically or colorimetrically. 
Unless the chamber has been used within five days or the nozzle becomes clogged, immediately before the test and with the exposure chamber empty, adjust all test parameters to those required for the test.    c. Chamber operation verification
Maintain these conditions for at least one 24-hour period or until proper operation and salt fog collection can be verified.  
To verify the chamber is operating properly, measure the salt fog fallout after 24 hours. Monitor and record the test chamber temperature.
Figure 509.6-3. Variations of density of salt (NaCl) solution with temperature
Figure 509.6-3. Variations of Density of Salt (NaCl) Solution with Temperature
Table 509.6-II. Temperature versus density data
Table 509.6-II. Temperature Versus Density Data
All items require a pretest checkout at room ambient conditions to provide baseline data.  Conduct the checkout as follows: Pretest Standard Ambient Checkout
Step 1. Prepare the test item in its required configuration in accordance with Part One, paragraph 5.8.1. 
Step 2. Record the room ambient temperature and humidity to determine if within standard ambient. 
Step 3. Conduct a complete visual examination of the test item with attention to:
(1) High-stress areas.
(2) Areas where dissimilar metals are in contact.
(3) Electrical and electronic components – especially those having closely spaced, unpainted or exposed circuitry.
(4) Metallic surfaces.
(5) Enclosed volumes where condensation has occurred or may occur.
(6) Components or surfaces provided with coatings or surface treatments for corrosion protection. 
(7) Cathodic protection systems; mechanical systems subject to malfunction if clogged or coated with salt deposits.
(8) Electrical and thermal insulators.
Note: Consider partial or complete disassembly of the test item if a complete visual examination is required.   Be careful not to damage any protective coatings, etc. during disassembly or reassembly.
Step 4. Document the results. (Use photographs, if necessary.)
Step 5. Conduct an operational checkout in accordance with the test plan, and record the results for compliance with Part One, paragraph 5.9.
Step 6. If the test item meets the requirements of the test plan or other applicable documents, proceed to Step 1 of the test procedure below.  If not, resolve any problems and restart the pretest standard ambient checkout at the most reasonable step above.
Step 1. With the test item in the chamber, adjust the test chamber temperature to 35 °C (95 °F), and condition the test item for at least two hours before introducing the salt fog. 4.5.2 Procedure
Step 2. Continuously atomize a salt solution of a composition as given in paragraph into the test chamber for a period of 24 hours or as specified in the test plan (see paragraph 2.2.3).  
During the entire exposure period, measure the salt fog fallout rate and pH of the fallout solution at least at 24-hour intervals 3/.  Ensure the fallout is between 1 and 3 ml/80 cm2/hr with a pH between 6.5 and 7.2.
Step 3. Dry the test item at standard ambient temperatures and a relative humidity of less than 50 percent for 24 hours, or as otherwise specified (see paragraph 2.2.3).  Minimize handling the test item or adjusting any mechanical features during the drying period.
Step 4. If the 48/48-hrs option has been chosen, proceed to Step 5.  Otherwise, at the end of the drying period, repeat steps 1 to 3 at least once.
Step 5. After completing the physical and any electrical checkouts,  document the results with photographs. See paragraph 5 for analysis of results.   
If necessary to aid in the follow-on corrosion examination, Use a gentle wash in running water that is at standard ambient conditions, conduct the corrosion examination, and document the results with photographs.
Step 6. Visually inspect the test item in accordance with the guidelines given in paragraph

MIL-STD-810G salt fog test equipment plays a crucial role in ensuring the durability and reliability of products exposed to salt-laden environments. By complying with the stringent requirements outlined in MIL-STD-810G, manufacturers can produce robust equipment capable of withstanding corrosive conditions. The salt fog test helps identify weaknesses, leading to improvements in design, materials, and coatings.

By investing in high-quality salt fog test equipment, manufacturers can reap the benefits of enhanced product reliability, cost savings, and increased customer confidence. Embracing the testing standard is crucial for industries seeking to deliver superior quality products in today’s competitive market. Proof by facts, This proactive approach ensures that products withstand harsh conditions and meet the highest industry standards for longevity and performance.

In addition to the guidance provided in Part One, paragraphs 5.14 and 5.17, the following information is provided to assist in the evaluation of the test results. 5. ANALYSIS OF RESULTS
a. Physical. Salt deposits can cause clogging or binding of mechanical components and assemblies.  The extent of any deposits resulting from this test may be representative of those induced by anticipated environments.
b. Electrical. Salt deposits could cause electrical malfunctions.
c. Corrosion. Analyze  any  corrosion  for  its  immediate  and  potential  long-term effects  on  the  proper functioning and structural integrity of the test item.
Note: Moisture remaining after the 24-hour drying period could cause electrical malfunctions.  If so, attempt to relate any malfunctions to that possible in service.

The MIL-STD-810G salt fog test equipment plays a significant role in several industries, catering to their specific needs. Its wide applicability makes it indispensable in various sectors. From automotive to aerospace, defense to electronics, and marine to telecommunications, the salt fog test is crucial for ensuring the reliability of products and components. By using MIL STD 810 salt spray test apparatus, companies can evaluate the resistance of their products to salt fog, identifying potential vulnerabilities and enhancing their overall reliability.

Salt fog testing helps assess the resistance of automotive components to corrosion in coastal or saline environments. It ensures the durability and longevity of vehicle parts exposed to harsh conditions, such as chassis, exhaust systems, and electrical connections. Automotive Industry: Application Scenarios for MIL STD 810G Salt Fog Test Equipment:
Saltwater and salt-laden air pose significant challenges to marine and offshore equipment. MIL-STD-810G salt fog testing helps evaluate the performance and longevity of materials used in shipbuilding, offshore platforms, and underwater infrastructure. Marine and Offshore Equipment:
Aerospace and defense industries rely on MIL-STD-810G salt fog tests to ensure the reliability of aircraft, missiles, and military equipment operating in coastal, humid, and corrosive environments. Salt fog testing helps identify potential vulnerabilities and design robust solutions. Aerospace and Defense:
Electronic devices and telecommunication equipment exposed to coastal or industrial environments need to be resistant to corrosion. Salt fog testing ensures that these devices maintain functionality and reliability, reducing maintenance costs and downtime. Electronics and Telecommunications:
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