4.1 Test Facility
- a. For construction of the chamber, supporting racks, and atomization equipment use materials inert to the acid solution being sprayed, and that will not cause electrolytic corrosion with material with which it comes in contact.
- b. Ensure the test chamber has a waste collection system so that all waste material can be tested prior to disposal. Dispose of any material determined to be hazardous waste in accordance with local, state, and federal regulations.
- c. Do not reuse acidic test solution drippings from the walls and ceilings of the chamber and from the test item. Vent the exposure chamber to prevent pressure buildup.
- d. Use a chamber capable of maintaining temperatures in the exposure zone at 35 ± 2 °C (95 ± 4 °F). Continuously control this temperature during the test. Do not use immersion heaters within the chamber exposure area for the purpose of maintaining the temperature within the exposure zone.
- e. Use an acid solution reservoir and dispenser made of material that is non-reactive with the acid solution, e.g., glass, hard rubber, or plastic. The reservoir provides a continuous supply to a tank normally (but not necessarily) situated inside the test section in which the acid solution level is held reasonably constant. The atomizers are connected to this tank.
- f. Use a chamber with a means for injecting the acid solution into the test chamber and with an input air humidifier to minimize clogging of the nozzles. Use atomizers of such design and construction as to produce a finely divided, wet, dense fog. Use atomizing nozzles and a piping system made of material that is non- reactive to the acid solution. Use a facility designed to provide the required atomization distribution and fallout.
- g. Use a test setup that includes a minimum of 2 fallout collection receptacles. One is to be 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. If multiple nozzles are used, the same principles apply. Place the receptacles so that they are not shielded by the test item and will not collect drops of solution from the test item or other sources.
- h. Constant air pressure for the continuous, uniform atomization of the acid solution using a compressed air supply, and produce a fallout such that each receptacle collects from 1 to 3 ml (0.03 0.10 oz) to of solution per hour for each 80 cm² (12.4 in.²) of horizontal collecting area (10 cm (3.9 in.) diameter).
4.2 Controls
- a. Compressed air. Preheat the oil and dirt-free compressed air used to produce the atomized solution (to offset the cooling effects of expansion to atmospheric pressure), and pre-humidify it such that the temperature is 35 ± 2 °C (95 ± 4 °F), and the relative humidity is in excess of 85 percent at the nozzle (see Table 518.2-I)
- b. Preheating. Heat the acid solution to within ± 6 °C (± 11 °F) of the test section temperature before injection into the test section.
- C. Test section air circulation. Use an air velocity in the test chambers that is minimal (essentially zero).
| Air Pressure (kPa(psi)) | 83 (12) | 96 (14) | 110 (16) | 124 (18) |
|---|---|---|---|---|
| Preheat temperature (°C (°F)) (BEFORE ATOMIZING) | 46 (115) | 47(117) | 48(118) | 49(120) |
MIL-STD-810H METHOD 518.2
4.3 Test Interruptions
Test interruptions can result from two or more situations, one being from failure or malfunction of test chambers or associated test laboratory equipment. The second type of test interruption results from failure or malfunction of the test item itself during operational checks.
4.3.1 Interruption Due To Chamber Malfunction
- a. General. See Part One, paragraph 5.11 of this Standard.
- b. Specific to this Method.
- (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. 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.
4.3.2 Interruption Due To Test Item Operation Failure
Failure of the test item(s) to function as required during operational checks presents a situation with several possible options.
- 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.
4.4 Test Setup
- a. General. See Part One, paragraph 5.8.
- 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.
4.5 Test Execution
The following steps, alone or in combination, provide the basis for collecting necessary information concerning the test item in an acidic atmosphere environment.
4.5.1 Preparation for Test
4.5.1.1 Preliminary Steps
- a. Prepare a test solution as specified in paragraph 2.4.4.
NOTE: MAKE THE SOLUTION BY ADDING ACID TO WATER, NOT VICE VERSA
WARNING: Refer to the supplier’s Material Safety Data Sheet (MSDS) or equivalent for health hazard data.
Strong acids are hazardous, and the solution to be used is harmful to people and clothing. Operators carrying out the test must take suitable precautions, and use personal protective equipment (PPE).
- (1) Do not enter the chamber during atomization. Before entry after atomization, purge the chamber with clean air to a level that will satisfy local safety requirements. Continue purging at intervals if necessary to ensure the concentration of noxious fumes remains at a suitably low level.
- (2) Wear a suitable respirator and/or eye protection. Use rubber gloves to handle materiel.
- b. Chamber operation verification: Immediately before the test and with the exposure chamber empty, adjust all test parameters to those levels required for the test. Maintain these conditions for at least one 24-hour period (or until proper operation and fallout collection can be verified). With the exception of fallout rate, continuously monitor all test parameters to verify that the test chamber is operating properly.
- c. Conduct an operational checkout in accordance with the test plan and record the results for compliance with Part One, paragraph 5.9. Handle the test item as little as possible, particularly on the significant surfaces, and prepare it for test immediately before exposure. Unless otherwise specified, use test items free of surface contamination such as oil, grease, or dirt that could cause dewetting. Do not include the use of corrosive solvents, solvents that deposit either corrosive or protective films, or abrasives other than pure magnesium oxide in the cleaning methods.
4.5.1.2 Pretest Standard Ambient Checkout
All items require a pretest checkout at room ambient conditions to provide baseline data. Conduct the checkout as follows:
- Step 1 Prepare the test item in its required configuration in accordance with Part One, paragraph 5.8.1.
- Step 2 Conduct a complete visual examination of the test item with attention to:
- (a) High-stress areas.
- (b) Areas where dissimilar metals are in contact.
- (c) Electrical and electronic components - especially those having closely spaced, unpainted or exposed circuitry.
- (d) Metallic surfaces.
- (e) Enclosed volumes where condensation has occurred or may occur.
- (f) Components or surfaces provided with coatings or surface treatments for corrosion protection.
- (g) Cathodic protection systems; mechanical systems subject to malfunction if clogged or coated with salt deposits.
- (h) 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.
MIL-STD-810H
METHOD 518.2
Step 3 Document the results. (Use photographs, if necessary.)
Step 4 Conduct an operational checkout in accordance with the test plan and record the results for compliance with Part One, paragraph 5.9.
Step 5 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.
4.5.1.3 Procedure
Step 1 With the test item installed in the test chamber in its storage configuration (or as otherwise specified in the requirements documents), adjust the test chamber temperature to 35 °C (95 °F), and temperature condition the test item for at least 2 hours before introducing the acid solution.
Step 2 Expose the test item to one of the two following severities as specified in the test plan. (See paragraph 2.4.2.) During either the (a) or (b) options shown below, continuously atomize the acidic solution (of a composition as given in paragraph 2.4.4). During the entire exposure period, measure the acidic solution fallout rate and pH at least at 24-hour intervals (Recommend more frequent intervals. Repeat the interval if fallout quantity requirements are not met). Ensure the fallout is between 1 and 3 ml/80cm2/hr.
(a) Four 2-hour exposure periods with 7 days storage after each.
(b) Three 2-hour exposure periods with 22 hours storage after each.
Step 3 At the completion of Step 2, stabilize the test item at standard ambient conditions.
Step 4 Using appropriate protective clothing, visually examine the test item to the extent practical.
Step 5 If required, place the test item in an operational configuration and conduct an operational check of the test item. See paragraph 5 for analysis of results.
Step 6 If required, test items may be cleaned by rinsing with a dilute sodium bicarbonate solution (to neutralize any acidic residue), followed by distilled/deionized water, and dried by the application of heat (up to 55 °C (131 °F)), where this is acceptable, or by other means. Collect the rinse water and check it for hazardous substances prior to disposal (see paragraph 4.1b also).
Step 7 At the end of this test, and in conformity with the requirements documents, examine the test item for corrosion and deterioration of parts, finishes, materials, and components. Document the results.