Salt Spray or Salt Fog Testing Chamber
Salt Spray Testing is governed by ASTM-B-117, and the following information is the basic information for maintaining the unit. Salt Spray and Salt Fog are the same test.
Fill humidifying tower with clean distilled water. Maintain water level in tower at capacity. This requires topping off every two or three days. The temperature of the tower air shall be between 114 to 1220F. The temperature gage is found on top of the tower and calibrated. Monitor temperature and record twice daily, morning and evening. The temperature will vary with tower fluid level, and incoming air pressure. It is therefore important to keep level and air pressure as constant as possible.
The compressed air supply to the tower is controlled by a regulator-filter unit Model Number 4Z028. The air pressure shall be kept between 10-25 psi. The air pressure directly controls the collection rate of the fog condensate within the chamber. Read the air pressure at the tower pressure gage which is calibrated and is next to the temperature gage. Do not set pressure with regulator gage. Record pressure once a day.
Fill the salt water reservoir with 5% 11 part (by wt.) salt water. Make this solution with deionized water and reagent grade salt (no more than .005% impurities).
The specific gravity (S.G.) shall be between 1.026 - 1.040. the S.G. will be checked at each filling and will be recorded daily by measuring the S.G. of the collected (post atomized fluid).
The collection rate will be no less than 1.0 ml per 24 hour period and no more than 2 ml per 24 hour period. The condensate collectors are positioned at the chamber corners, there are two. Each consisting of a 100 ml graduated cylinder with collection funnels, with an area (major) of approximately 80 cm2. Place collectors in corners diagonally. Read and record collection rates daily. Do not allow samples or sample racks to drip into collectors. Collection time shall be no less than 16 hours.
The pH of the salt solution will be measured electrometrically at ambient temperature (250C) with a pH meter (calibrated). The pH will be obtained from the collected post atomized condensate and recorded daily. The pH will be between 6.5 and 7.2. Deviation from this range will require adjustment with CP Sodium Hydroxide or CP Hydrochloric Acid. Make sure to check calibration of meter with buffer standards prior to measurement of test fluid.
The test chamber is to be maintained at 92-97°F. This unit is encased by an outer cell. Hot air circulated between the structures heats the test volume to the required mean temperature. The use of immersion heaters to heat the chamber is not allowed. The temperature gage is at front and center of the cabinet lid and is calibrated. The temperature shall be recorded twice per day along with the tower temperature readings.
The concentration of salt shall be checked and logged daily, with a hydrometer that has been tested in accordance with ASTM E126. The specific gravity will be maintained within the range of 1.0255 to 1.0400. These readings shall be logged on the Salt Spray Worksheet.