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2 Four Kinds Of Judgment Methods Of Salt Fog Test Results

Salt Spray Testing

SCOPE: this standard prescribe the conditions required in salt spray testing for specification purpose. It dose not prescribe the type of the specimen or exposure periods to be used for a specific product, nor the interpretation to be given to the results.

The salt spray of our company can do the salt spray test as follows.

 

APPARATUS:

2.1 the apparatus required for salt spray testing consists of a fog chamber, a salt solution reservoir, a supply of suitably conditioned compressed air, one or more atomizing nozzles, specimen supports, provision for heating the chamber, and necessary means of control. The size and detailed the conditions obtained meet the requirements of this method.

2.2. drop of solution which accumulate on the celling or cover of the chamber shall not be permitted to fall on the specimens being tested.

2.3. drops of solution which fall from the specimens shall not be returned to the solution reservoir for respraying.

2.4. materials of construction shall be such that they shall not affect the corrosiveness of the fog, nor be themselves corroded by the fog.

TEST SPECIMENS: the type and number of test specimens to be used, as well as the criteria for the evaluation of the test results, shall be defined in the specifications covering the material or product being tested of shall be naturally agreed upon by the purchaser and the supplier.

 

PREPARATION OF TEST SPECIMENS  

3.1. metallic and metallic-coated specimens shall be suitably cleared. The clearing method shall be optional depending on the nature of the surface and the contaminants, except that it shall not include the use of abrasives other than a parts of pure magnesium oxide nor of solvents which are corrective or will deposit either corrosive or protective films. The use of a nitric  acid solution for the chemical cleaning, or passivation, of stainless steel specimens is permissible when agreed upon by the purchaser and the supplier. Care shall be taken that specimens are not recontaminated after cleaning by excessive

or careless handling.

3.2. specimens for evalustion of paints and other organic coasting shall be prepared according to applicable specification for the material being tested, or as agreed upon by the purchaser and applier. Otherwise the specimens shall consist of steel meetion the requirements of the methods for preparation of steel panels for testion paint, varnish, lacquer, and relate products and shall be cleaned and prepared for coaction according to procedure A OF ASTM D609.  3.3. specimens coated with paints of nonmetallic coactions shall not be cleaned of handled excessively prior to test. Whenever it is desired to determine the development of corrision from an abraded area in the paint of organic coation, a scratch of scribed line shall be made through the coation with a sharp instrument so as to expose the underlying metal before testing, the conditions of making the scratch shall be agreed upon between the purchaser and supplier.

3.5. unless otherwise specified, the cut edges of plated, coated, or duplex materials and areas containing identification marks or in contact with the racks of supports, shall be protected with a suitable coating stable under the conditions of the test, such as ceresin wax.

 

POSITION OF SPECIMENS DURING TEST  

the position of the specimens in the salt spray chamber during the test shall be such that the following conditions are met.

4.1.unless otherwise specified, the specimens shall be supported or suspended between 15 and 30 degrees from the vertical and preferably parallel to the principle direction of horizontal flow of fog through the chamber, bassed upon the dominant surface being tested.

4.2. each specimen shall not contact each other or any metallic material of any material capable of acting as a wick..

4.3. each specimens shall be so placed as to permit free setting of fog on all specimens.

TEST SOLUSION  the salt solution shall be prepared by dissolving 5g of salt per every 95ml of distilled water of water containing not more than 200 ppm of total solids. The salt used shall be sodium chloride substantially free of nickel and copper and containing on the dry basis not more than 0.1 percent of sodium iodide and not more than 0.3 percent of total impurities.

 

CONDITIONS IN THE TEST CHAMBER  

5.1. TEMPERARTURE  the exposure zone of the salt chamber shall be maintained at 35 plus 1.1 or minus 1.7℃. the temperature within the exposure zone of the closed cabinet shall be recorded at least twice a day at least 7 hours apart.

5.2. ATOMIZATION AND QUANTITY OF FOG at least two clean fog collectors shall be so placed within the exposure zone that no drops of solution from the test specimens of any other source shall be collected, the collectors shall be placed in the proximity of the test specimens, one nearest to any nozzle and the other farthest from all nozzles. The fog shall be such that for each 80 C㎡  horizontal collection area there will be collected in each collector from 1.0 to 2.0 mL of solution per hour based on an average run of at least 16 hours. The sodiun chloride concentration of the collected solution shall be 5±1 percent mass. The pH of the collected solution shall be 6.5 to 7.2. the pH measurement shall be made electrometrically of colorimetrically using Bromthymol blue as the indicator.

5.3. the nozzle of nozzles shall be so directed or baffled that none of the spray can impinge directly on the test specimens.

5.4.dilution andevsporation of condensate should be avoided.

 

CONTINUIY OF TEST  

unless otherwise specified in the specifications covering the material of 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 operation continuously except for the short daily interruptions necessary recordings as described in section8. operations shall be so scheduled that these interruptions are held to a minimum.

 

PERIOD OF TEST. 

The period of test shall be as designated by the specification covering the material of product being tested, or as mutually agreed by the purchaser and supplier.

 

CLEANING OF TESTED SPECIMENS  

unless otherwise specified in the specification covering the material of product being tested, specimens shall be treated as follows at the end of the test.

8.1 the specimens shall be carefully removed from the chamber.

8.2 specimens shall be gently rinsed in clean running warm water to remove salt deposits from their surface, and then immediately dried. Drying shall be accomplished with a stream of clean, compredded air at a gage pressure of 240 to 25 kPa.

 

CVALUATION OF RESULTS  a carefully and immediate examination shall be made for the extent of corrosion of the dry test specimens of for other failure as required by the specification covering the material or product being tested or by agreement between the purchaser and supplier.

 

RECORDS AND REPORTS   

The following information shall be recorded, unless otherwise prescribed in the specification covering the material of product being tested.

10.1 type of salt and water used in preparing the salt solution.

10.2 all readings of temperature within the exposure zone of the chamber.

10.3 daily records of data obtained from each fog collecting device, including the following.  10.4 volume of salt solution collected in millilitre per hour per 80 C㎡

10.5 concentration or specific gavity at 35℃of solution collected.

10.6 pH of collected solution.

10.7 type of specimen and dimension thereof or part number of description of part.

10.8. method of cleaning specimens before and after testing.

10.9 method of supporting of suspending article in the salt spray chamber.

10.10. description of protection used as required in section 4.

10.11 exposure period.

10.12 interruptions in test, cause and length of time.

10.13 results of all inspections.

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