Climatic Chambers for Standard TPJR-52-252 Resistance To Neutral Salt Spray Corrosion Testing
This test procedure applies to all JLR vehicles and defines an accelerated test for determining the resistance to neutral salt spray of ferrous and non-ferrous metals, inorganic and organic materials, coatings, components and sub-assemblies. It is based on ASTM B117. This standard needs a climatic chamber--salt spray chamber.
This test procedure defines the duration of the exposure period which is stipulated within this test procedure as a specific test requirement in support of the JLR eFDVS Corrosion Requirements. The performance requirements and any specific sample preparation shall be as defined in the relevant materials or product standard.
A valid risk assessment must be in place before this test is conducted.
This document must be reviewed at least every three years from the date of the last review or update.
A salt spray test cabinet that satisfies both the test conditions stipulated within ASTM B117 and this test procedure.
Position of samples during test:
Where the geometry permits, samples shall be supported or suspended between 15 degrees and 30 degrees from the vertical and with any significant surface parallel to the principal direction flow of fog. Components and sub-assemblies, where practicable, shall be mounted in the attitude in which they will be assembled in service.
Samples shall be at least 30mm apart and 35mm from a chamber wall. Contact between independent samples must be avoided.
Samples shall be placed so as to permit free settling of fog on all samples but also to avoid salt solution from one sample dripping onto another.
Salt solution:
Prepare a 5%±1% by weight solution using sodium chloride to BS 998 with distilled or deionised water.
The PH of the salt solution when measured electrometrically shall be such that when atomised at 35℃, the collected solution shall be in the PH range of 6.5 to 7.2. Adjustment of the PH can be carried out by the addition of dilute hydrochloric acid (HCI) or sodium hydroxide (NaOH), analar grade, to the salt solution reservoir.
The PH of the salt solution after atomisation at 35℃ will be less acidic than that of the initially prepared solution at room temperature due to the loss of carbon dioxide at the higher temperature. Any adjustments of PH of the salt solution at room temperature shall, therefore, take this into account.
Test Conditions:
Temperature--the exposure zone of the salt spray fog chamber shall be maintained at 34℃±2℃.
Quantity of salt fog--at least two clean fog detectors shall be placed in the exposure zone in the proximity of the test specimens, one near to the nozzle and the other as far as possible from the nozzle. They shall be positioned such that no solution falling from the test samples shall be collected.
The fog shall be such that for each 8000mm² of horizontal collecting area, there will be collected (in each container), 1.0 to 2.0ml of solution per hour, determined over an operating period of not less than 16 hours.
The sodium chloride concentration of the collected solution shall be 5%±1% by weight (specific gravity of solution 1.0255 to 1.0400 at 25℃). The PH of the collected solution, when measured electrometrically, shall be in the range of 6.5 to 7.2.
Standard laboratory funnels having a diameter of approximately 100mm, and with their stems inserted through stoppers into graduated measuring cylinders, form suitable collecting devices.
Sample Preparation:
Prepare the sample for test in accordance with the requirements of the appropriate material or product standard.
Paints and other organic coatings shall be prepared in accordance with the applicable materials specifications.
Samples that require sectioning shall have all the raw edges suitably sealed so to avoid unnecessary corrosion bleed.
Test Method:
After preparation of the samples expose the samples in the neutral salt fog chamber for the specified period detailed within the relevant requirement.
Inspect the samples and check on the operation of the chamber at suitable intervals, at which times the positions of the samples may be conveniently altered, if required. Opening of the chamber shall be restricted to the minimum time and frequency necessary to carry out the above operations, with a maximum of 15 minutes twice daily permissible.
Remove the samples, wash gently in distilled or deionised water of maximum temperature 38℃ and dry off using absorbent paper wipes.
Examine the surfaces immediately for any corrosion of the substrate, or any other deleterious effects, in accordance with the acceptance criteria defined in the relevant materials or product standard.
Calibration of test equipment:
In order to assess the reproducibility of results from test apparatus, it is necessary to carry out calibration procedures:
Test pieces 1.00mm±0.25mm thick and at least 50mm×80mm cut from cold rolled strip or sheet in accordance with BS 1449 Part 1 grade CS1 or CR1. The surface shall be free from pores, marks, scratches and any other detrimental effects.
The test pieces shall be cleaned, as appropriate, and weighed to the nearest milligram using an analytical balance.
The rear side of the test pieces shall be protected by a suitable method, e.g. application of a self-adhesive plastic foil or wax coating.
The test pieces shall be positioned in the cabinet with the non-protected face uppermost and at an angle of 20°±5° to the vertical. A minimum of four test pieces shall be used and they must be located within the relevant exposures zone of the cabinet such that the distribution effects are measured.
The test duration shall be 96 hours. At the end of the test period, the protective coating on the rear side shall be taken off and the corrosion products removed by one of the following methods.
Blast with equipment and an abrasive media which has been shown to produce negligible metal loss on uncorroded test pieces.
After stripping, the test pieces shall be thoroughly cleaned by rinsing with water followed by acetone. The test pieces shall be dried and re-weighed to the nearest milligram.
Calculate the weight loss in g/m².
The test equipment shall be deemed to be functioning satisfactorily if the average weight loss of the panels is 130g/m²±20g/m². No individual test panel shall exhibit a weight loss of greater than 150g/m² or less than 110g/m².
The test equipment shall be calibrated at least once every four weeks of cintinous operation.
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