Salt spray test parameters

A. astmb633.htmlb117.html" --> should have all of the information you need with regards to maintaining the salt fog conditions. When evaluating the results of corrosion tests, there are a number of standards to use. The following is a partial list:

ASTM D610 Standard Test Method for Evaluating Degree of Rusting on Painted Steel Surfaces

ASTM D714 Standard Test Method for Evaluating Degree of Blistering of Paints

ISO 4628-1PAINTS AND VARNISHES - EVALUATION OF DEGRADATION OF COATINGS - DESIGNATION OF QUANTITY AND SIZE OF DEFECTS, AND OF INTENSITY OF UNIFORM CHANGES IN APPEARANCE - PART 1: GENERAL INTRODUCTION AND DESIGNATION SYSTEM

ISO 4628-2PART 2: ASSESSMENT OF DEGREE OF BLISTERING
ISO 4628-3PART 3: ASSESSMENT OF DEGREE OF RUSTING
ISO 4628-4PART 4: ASSESSMENT OF DEGREE OF CRACKING
ISO 4628-5PART 5: ASSESSMENT OF DEGREE OF FLAKING
ISO 4628-6PART 6: RATING OF DEGREE OF CHALKING BY TAPE METHOD
ISO 4628-7PART 7: ASSESSMENT OF DEGREE OF CHALKING BY VELVET METHOD
ISO 4628-10PART 10: ASSESSMENT OF DEGREE OF FILIFORM CORROSION

A. ASTM B117 includes a section on records and reports. That information applies to the test conditions only. The test requires water which meets ASTM D1193 Type IV. Using this water will not guarantee the correct pH since that is very much dependent upon the proper mixture of salt and water, as well as the salt itself. Checking the pH of the collected solution is required by B117. The results and evaluations of the samples are usually outlined in the material specification. For example, an automotive company may indicate that 5% red rust is allowable, while another may require less than 5%. Usually results are recorded at the end of the test, but that can vary with the material specification.

As Toby already indicated, there are a number of standards which describe a rating scale.

A. You absolutely have to check both the makeup tank and the collected spray. They will not be the same pH as the collected solution will take up some carbon dioxide from the air and change the collected pH. The tank pH has to be maintained at a pH that will allow for the correct "collected" sample pH. A final note, don't look for an easy way out. If you take that approach, you are not in compliance with the specification and thus can not certify to it!

A. B117 requires that you check the pH of the collected solution. Since it usually changes during atomization, the only way you will know the pH at which to start your make-up solution is to check that, too. Using distilled or deionized water doesn't guarantee that the pH will be correct.

A. Hi, Chidambar. I believe that spec is also known as IEC 60068-2-11 Ka. We've linked to a place you can get it. Good luck.

Regards,

A. MIL-STD-1312-1, "Fastener Test Methods. Method 1, Salt Spray"

A. Hi Steven,

I would hope that after 40 hours you wouldn't see any red rust, it would indicate either an inadequate thickness of zinc or poor quality plating!

At the end of the day you have to make the call about what is acceptable to you. Your acceptance standard will depend on how and where you are using the coating.

In aerospace we tend to want a much higher standard of corrosion resistance than say the automotive industry, so where automotive may look for 48 hours resistance to red rust aerospace would be looking for 96 hours to white and probably 168 hours to red rust.

A. Hello Steven,

If you see the posts above, you will see one written by Toby Padfield. He listed some of the standards to assess corrosion test results. 5% maximum corrosion is not a bad criterion, you should talk with your client to clarify how much is OK or not OK.

Hope this helps you! Good luck!