技术文章

SAE J2334 International surface vehicle standard（盐雾试验标准二）

2.1.4.1 Reproducibility and Repeatability information concerning this test method is discussed in SAE Paper 970734. See Reference 14.

3. Definitions
3.1 Cosmetic Corrosion－Corrosion that occurs as a result of the breakdown or damage to a coating system. Typically, this type of corrosion does not impact functiong but does compromise appearance.

3.2 General Corrosion－Corrosion of a component that is typically bare（no organic coating）. Corrosive attack is uniform in nature and distributed over "large" areas.

3.3 Scribe Creepback－Coating creepback resulting from corrosion and undercutting from the scribe line. A scribe is a controlled simulated damage site designed to represent a scratch or chip.

3.4 Corrosion Coupons－Samples of bare metals, that are used to monitor and compare the corrosivivty of laboratory corrosion tests in terms of mass-loss.

3.5 Test Controls－Components（i.e., test panels,coupons,parts,etc.） which have been previously tested and/or correlated. They can be used to control the test conduct and compare the test results（also assist in evaluating reproducibility and repeateability）.

4. Equipment and Test Materials
4.1　Test Cabinets－Test cabinet（s） with the ability to obtain and maintain the following environmental conditions （Reference SAE J1563, ASTM D 1735, and ASTM D 2247）.

a. 50℃±2℃ and 100% Relative Humidity－The 100% relative humidity wet-stage condition can be achieved by use of one of the three methods shown as follows. Whichever method is employed, test samples and controls are required to be visibly moist/wet.

1. Wet-bottom method according to ASTM D 2247-except that the temperature shall be 50℃±2℃.
2. Water fog method according to ASTM D 1735, except that the collection rate is reduced from a range of 1.5 to 3 mL/h to 0.75 to 1.5 mL/h. The use of this method requires that the collection rates be documented.
3. Steam （vapor） generator method.

NOTE— The majority of the development of this specification was performed using the Wet-bottom method of humidity generation. This method was used as the basis when comparing other methods of humidity generations as well as other variables.

b. 60℃±2℃ and 50% Relative Humidity ±5%. Additional equipment will be required to maintain the 50% relative humidity condition.

Air circulation must be sufficient to prevent temperature stratification and allow drying of test parts during the dry-off portion of the test cycle.

Air circulation can be obtained through the use of a fan or forced air.

4.2 Salt Solution Application－The samples must be subject to an application of salt solution by use of one of the three methods shown as follows. Whichever method is employed, test samples and controls are required to be visibly moist/wet during the entire 15-minute interval of each test cycle.

   0.5% NaCl
   0.1% CaCl2
   0.075% NaHCO3
a. Immersion Method－Test specimens are to be immersed in the salt solution
for a 15-minute interval of each test cycle.

b. Spray Method－A periodic or continuous direct impingement spray of the salt solution over the 15-minute interval that ensures the test specimens are kep wet for the entire 15-minute interval. Avoid a high intensity （pressure） spray that may affect test results. （Note 5） Both direct solution displacement and atomized spray are suitable for this method.

c. Air Atomized Fog Method－Applications of the salt solution to the test specimens by a 15-minute exposure to atomized fog provided the fog collection rate is 2 to 4 mL/h instead of 1 to 2 mL/h （collection rate as defined in ASTM D 1735）. The use of this method requires that the collection rates be documented.

NOTE 1－"Either the CaCl2 or NaHCO3 material must be dissolved separay in Dl water （Reference ASTM D 1193 Type IV） and then added to the solution of other materials. If all solid materials are added at the same time in a "dry" state, an insoluble precipitate may result. If a precipitate forms and a spray application is used to apply the solution, it may be necessary to remove the precipitate to avoid clogging of nozzles（i.e., filter or siphone solution）. Any filter media used must be inert to the solution being used. A 20 to 100 micron cotton or nylon mesh filter would be suitable. Do not attempt to dissolve the precipitate by adding acid.

NOTE 2－Measure and record pH of the salt solution prior to the start of test and on a weekly basis thereafter （Reference ASTM E 70-90）. Do not attempt to adjust the pH with any form of buffers.]

NOTE 3－The majority of the development of this specification was performed using he immersion method of salt solution application. This method was used as the basis when comparing other methods of salt solution applications as well as other variables.

NOTE 4－A freshly prepared test solution will have a conductivity of 10 to 12 ms at 25℃±2℃. Measure and record the conductivity （in units of ms） of the salt solution after mixing, prior to the last amount being used, and as needed to ensure that the conductivity of the solution remains between 10 to 12 ms at 25℃.

NOTE 5－Careful attention should be paid to the spray method to avoid a high intensity apray that may affect test results by removal of the corrosion product, removal of the coating or driving solution into the corrosion products.

It is recommended that the test solution be changed weekly and that agitation/stirring of the solution be done prior to the salt solution application.