Salt fog method is applied to determine the effectiveness of protective fog coatings and finishing materials. It can also be applied to determine the effects of salt deposits on the physical and electrical aspects of the material.

MIL-STD 810G covers accelerated corrosion by using salt fog in Method 509.5. This method consists of 10 pages. This is one of the more common tests and is absolutely necessary for goods sold to the Navy or for use in coastal areas. Salt is one of the most common chemical compounds in the world. It is found in oceans and seas, atmosphere, ground surfaces and in lakes and rivers. It is impossible to avoid salt exposure.

Method 509.5 is intended to evaluate the effectiveness of protective coatings and coatings on materials. All unprotected metals will rust if they are not protected by a surface such as coating or paint. Finishes may also have holes or cracks that allow corrosion to reach the underlying material and cause corrosion. The method may also be applied to determine the effects of salt deposits on the physical and electrical aspects of the apparatus.

The effects of an abrasive environment are:

• Corrosion effects such as electrochemical reaction, stress corrosion and formation of acidic / alkali solutions
• Electrical effects such as deterioration of electrical material due to salt deposits, production of conductive coatings that cause short circuit and corrosion of insulating materials.
• Physical effects such as clogging or clogging of moving parts and blistering of the paint as a result of electrolysis at the bottom.

Only use Method 509.5 to assess the quality and effectiveness of protective coatings and varnishes for screening purposes. Coupons (samples) or final assembly can be evaluated. The method does not represent the natural environment, but is a good indicator of potential problem areas. In general, apply this Method only to material that may be significantly exposed to high levels of salt in the atmosphere, such as shipboard applications.

The method lists the six limitations as follows:

• There is no correlation between this test and the duration of exposure in the real world.
• A direct relationship between salt fog corrosion and corrosion from other environments has not been established.
• This test does not mean that the material will survive under all corrosive conditions.
• This test is not reliable for predicting the life of materials under corrosive conditions.
• The effects of moisture and fungal growth are not shown in this test.
• This test is not intended to be used for sample or coupon testing rather than assembly testing.

The method requires that a salt fog of% 5 (+ / -% 1) is produced and circulated (with minimum air velocity) around the product being tested. Condensation does not drip into test substances. This is a fog test, not a salt water exposure test. Although an alternative 24 hour test cycle (24 mist, 24 drying, 24 mist, 24 drying) has proven to be more destructive, it is recommended that the test last for 48 hours with 48 hour drying time. The test temperature was determined as 35 ° C, historically accepted and not necessarily indicative of the actual environment. Alternatively, suitable temperatures may be used.

SALT FOG TEST PROCEDURE

1. Step. While the test substance is in the chamber, adjust the temperature of the test chamber to 35 ° C and allow the test substance to stand for at least two hours before adding salt fog.
2. Step. Spray a composition given in paragraph 4.5.1.1b for a period of 24 hours or continuously into the test chamber as specified in the test plan (see paragraph 2.2.3). Measure the salt fog sputtering rate and pH of the sputter solution at least 24 hourly intervals over the entire exposure period. Ensure that the spray is between 4 to 1 ml / 3 cm80 / hour.

      3 steps. Dry the test substance at standard ambient temperatures and for 24 hours at less than 50 percent or relative humidity as otherwise specified (see paragraph 2.2.3). Minimize using the test substance or adjusting the mechanical properties during the drying time.

4. Step. If the 48 / 48-clock option is selected, proceed to Step 5. Otherwise, repeat steps 1 to 3 at least once at the end of the drying time.

My name is 5. Document the results with photographs after completing the physical and electrical checks. 5 for analysis of results. see paragraph. If it is necessary to assist in the follow-up corrosion inspection, use a gentle wash in running water under standard ambient conditions, carry out a corrosion check and document the results with photographs.

6. Step. Visually inspect the test item in accordance with the rules given in paragraph 4.5.1.2.

In general, test samples taken from the salt fog test should not be used in other tests. If only one sample is available or if a sample is to be reused for other tests, moisture and fungus growth test should be performed before the salt fog test and sand and dust test after the salt fog test.

After testing, the substance should be examined for physical, electrical and corrosion effects. There may be surprising results. We tested a back panel of a nickel-plated sample as compared to a zinc-plated. Apparently, the more expensive nickel had marked holes in the plating and failed miserably; the much cheaper zinc coating showed only mild surface corrosion without damaging the underlying metal.

EUROLAB® works with several customers to define test procedures as required by MIL-STD-810G to validate our demanding rack-mounted computer systems and displays.