1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW3286 Neutral Salt Spray (NSS) Test Copyright 2011 General Motors Company All Rights Reserved October 2011 Originating Department: North American Engineering Standards Page 1 of 4 1 Scope Note: Nothing in this standard supercedes applicable laws and
2、regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. The neutral salt spray test is typically used to evaluate the corrosion resistance of metallic substrates and the corrosion preventative properties of coati
3、ngs. 1.2 Foreword. This standard establishes test equipment and test specimen requirements for conducting the neutral salt spray test. The chamber operation and test procedures are based on ISO 9227. Clarifications to ISO 9227 requirements are defined below. 1.3 Applicability. The neutral salt spray
4、 test is typically used for quality control and process control evaluations and not for simulating field performance. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ISO 9227 2.2 GM Standards/Specifications. None
5、 3 Resources 3.1 Facilities. Laboratory (preferably with controlled ambient conditions). 3.2 Equipment. 3.2.1 Test Chamber. The apparatus shall consist of an environmental chamber, a suitable water supply conforming to ISO 9227 (section 3.1) requirements, provisions for humidification and heating of
6、 the chamber, and the necessary means of control along with the ability to maintain the following environmental conditions: 3.2.1.1 Chamber Temperature: 35 2 C (95 3 F). 3.2.1.2 Humidity 100% relative humidity (RH). 3.2.1.3 Humidification/Bubble Tower Temperature: May be adjusted such that the speci
7、fied operating conditions are met. 3.2.1.4 Humidification/Bubble Tower Pressure: May be adjusted such that the specified operating conditions are met. Note: Refer to ISO 9227, Annex A for schematic diagram of one possible design of test chamber. 3.2.2 Fog/Water Collection. Suitable collecting device
8、s include glass or plastic funnels with the stems inserted into collection vessels. Funnels with a diameter of 10 cm have an area of about 80 cm2. 3.2.2.1 At least two clean fog collectors shall be placed within the exposure zone so that no drops of solution from the test specimens or any other runo
9、ff source shall be collected. 3.2.2.2 The collectors shall be placed in the proximity of the test specimens. 3.2.2.3 Collection rates for each 80 cm2 of horizontal collection area should be in the range of 1.0 to 2.0 mL/h in each collector. Exposure zones for test specimens shall be established base
10、d on demonstrated conformance to the collection rate range. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3286 Copyright 2011 General Motors Company All Rights Reserved October 2011 Page 2 of 4 3.2.2.4 The pH o
11、f the collected solution must be in the range of 6.5 to 7.2, when measured at 25 3 C. It may be necessary to adjust the pH by adding hydrochloric acid or sodium hydroxide or sodium bicarbonate solution of analytical grade. 3.2.2.5 The specific gravity of the collected solution shall be 1.025 to 1.04
12、0 when measured at 25 3 C. Note: Test chamber parameters, collection rates, pH, and specific gravity shall be monitored and recorded daily (excluding weekends) during normal operation. 3.3 Test Vehicle/Test Piece. Not applicable. 3.4 Test Time. Typical: Calendar time: 1 to 42 days Test hours: 24 to
13、1000 hours Coordination hours: 1 to 4 hours 3.5 Test Required Information. Not applicable 3.6 Personnel/Skills. Not applicable 4 Procedure 4.1 Preparation. 4.1.1 Test Solution Preparation. The salt solution in percent (%) by mass shall be as specified below: Sodium Chloride (NaCl): 5% Note: Reagent
14、grade or food grade sodium chloride may be used. The purity of the sodium chloride shall meet ISO 9227 (section 3.1) requirements. Water must meet ISO 9227 (section 3.1) requirements. 4.1.2 Sample Preparation. 4.1.2.1 Samples shall be suitably cleaned, if necessary, prior to exposure. The cleaning m
15、ethod shall be optional depending upon the nature of the surface and the type of contaminants. The cleaning shall not include the use of abrasives or solvents which may compromise the test surface. 4.1.2.2 Cut edges, backs, and other test specimen imperfections shall be suitably coated or protected,
16、 per the discretion of the test engineer, or per agreement between the test engineer and the requester, prior to the initiation of the test. 4.1.2.3 Test specimens are generally oriented in the test chamber so that the dominant test surface is exposed to the salt fog at approximately 15 to 30 from v
17、ertical. Specimens may be oriented at other angles if agreed upon by the requester and the test engineer. 4.1.3 Chamber Preparation. Prior to initiation of testing, the salt solution and test chamber operating conditions, based on a minimum of 16 h, shall be met. 4.2 Conditions. 4.2.1 Environmental
18、Conditions. See 3.2. 4.2.2 Test Conditions. Deviations from the requirements of this standard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc. 4.3 Instructions. 4.3.1 Chamber Operation. Chamber operation shall be continuous for
19、 the specified test periods. “Continuous” testing is defined as testing that is interrupted only to allow for the daily collection of salt solution, to rearrange, remove, or introduce new test specimens, or to perform necessary chamber maintenance and repair. The number of interruptions shall be lim
20、ited to three in any 24 h period, and shall be approximately ten minutes in duration, where feasible. 4.3.1.1 Daily Chamber Activity. Record necessary parameters of chamber such as chamber temperature. Evacuate the chamber using safe operating and maintenance practices. Once chamber is evacuated the
21、 chamber can be accessed. Collect solution captured in each graduated cylinder. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3286 Copyright 2011 General Motors Company All Rights Reserved October 2011 Page 3 o
22、f 4 Add or remove samples as necessary. Samples should be placed in locations verified to be within specifications relative to solution collection rates. Restart chamber. Verify collected solution is within specification. Document solution parameters and adjust accordingly. 4.3.2 Test Duration. Dura
23、tion of test shall be per the applicable product or material specification, or per agreement between the requester and test engineer. 5 Data 5.1 Calculations. Not applicable. 5.2 Interpretation of Results. Evaluations (pre-test and post-test), rating methods, and acceptance criteria shall be specifi
24、ed within engineering documentation which includes: Material Specifications, Vehicle Technical Specifications, Subsystem Technical Specifications, Component Technical Specifications, and Part Drawings. 5.3 Test Documentation. 5.3.1 Test Equipment. 5.3.1.1 The following chamber parameters should be r
25、ecorded daily (excluding weekends): Chamber Temperature Humidification/Bubble Tower Temperature Humidification/Bubble Tower Pressure 5.3.2 Test Solution. The following information shall be recorded and available upon request: 5.3.2.1 Initial pH of each batch test solution. 5.3.2.2 Initial specific g
26、ravity of each batch test solution. 5.3.2.4 The following collected solution parameters should be recorded daily (excluding weekends): pH Specific gravity 5.3.3 Test Report. Test reports should include all pertinent test information. 6 Safety This standard may involve hazardous materials, operations
27、, and equipment. This standard does not propose to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 7 Notes 7.1 G
28、lossary. Not applicable. 7.2 Acronyms, Abbreviations, and Symbols. GSSLT Global Subsystem Leadership Team h hour mL milliliter RH Relative Humidity NSS Neutral Salt Spray 8 Coding System This standard shall be referenced in other documents, drawings, etc., as follows: Test to GMW3286 Provided by IHS
29、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3286 Copyright 2011 General Motors Company All Rights Reserved October 2011 Page 4 of 4 9 Release and Revisions This standard was originated in December 1999. It was first approve
30、d by Corrosion GSSLT in April 2006. It was first published in May 2006. Issue Publication Date Description (Organization) 1 MAY 2006 Initial publication. 2 OCT 2011 Five year refresh - converted from Test Method to Test Procedure. (Corrosion Global Subsystem Leadership Team) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
