Salt Spray Test -- ASTM B117 Operational Problems

A. First, empty and scrub your salt water reservoir: it could easily be the biological contamination.
Otherwise, perhaps your feed tubes from the salt reservoir to the bubble tower need to be replaced: tubing is pretty cheap.
The main problem I've encountered with salt spray chambers is copper contamination in the bubble tower coming from the copper compressed air line. The water in the tower acts as a filter, and if you have a greenish-white buildup on the cylindrical casing, you need to dismantle it and get that buildup off. It dissolves easily with paper towels soaked in dilute (25 - 50%) HCl laid on the buildup for about 10 minutes - wipe & repeat if necessary. Though the manufacturers recommendations don't cover it, one should drain and refill the bubble tower once monthly to avoid this possibility.
I don't believe the copper issue has anything to do with altering the pH, but it helps with multiple other problems - like premature or false corrosion of test panels.

A. Hi Alex, did you check whether there were drops from the cover falling into your collector? This is impossible if you got correct pH at nozzle but incorrect in your collector; as you know, the fog drops into collector directly and contacts nothing after going out from nozzle. Or did you collect fog with products been tested? If yes, whether there were drops from products fall into collector?

A. Hi Sankar. Although I haven't run a salt fog cabinet, I think it's some kind of measurement error. The specific gravity of pure water is 1.00 and it should be heavier with any salt in it.

Regards,

A. Tonya,
Use a calibrated temperature probe to verify that you are 95 °F. (A 10 °C increase in temperature will double the rate of corrosion.)

A. Adjust (lower) the pressure regulator on the airline.

? Hi Abdul. What is your response to Fauna's suggestion just above? Thanks.

Regards,

A. My guess would be copper contamination, probably from the air lines. Take an air filter off the line & swap the interior of the connecting pipe to check. If there's buildup, replace your piping. Also drain & clean your bubble tower, as it acts as a filter & gets contaminated.

A. Good day Olivia.

I too, had the same concern as I had designed racks for panels some years ago, and had arbitrarily chosen 1.5 inches separation based on monthly panel requirements and square footage of cabinet area.

According to NADCAP regulations regarding salt panel separation:

"10 inch panels @ 6 degrees from the vertical shield approx. 1.0 inches."
"6 inch panels @ 15 degrees from the vertical shield approx. 1.6 inches."

See ASTM B117, Section 7 "Position of Specimens During Exposure."
Hope this helps.
From a fellow salter.

Regards,

A. Good day Olivia.

Google "NADCAP Website" for programs, info...
There is a contact available.

Regards,

Good day Wil.

What a novel idea about the rack.
The only problem I can foresee, is Nadcap salt panel separation requires "10 inch panels @ 6 degrees from the vertical shield approx. 1.0 inches", and "6 inch panels @ 15 degrees from the vertical shield approx. 1.6 inches".
I had my racks fabricated and designated to accommodate variations in panel thicknesses.
Some Nadcap auditors do go to EXTREME length to discover observations, minors, and the dreaded majors.

Regards,

A. Hello all!

Sandy: I hope you solved this already, but if you haven't, I think the fog ejector may have some regulation (bigger or smaller drops, more or less salt water injection). If not, you may need to do it by modifying air pressure in the ejector.

Ray: Do you pre-humidify the air you inject? There is a saturation tower in almost every design of SST, so the air you inject is 100% relative humidity at 40 °C (it is my setting). You should verify this point! Let us know if you solved this!

Kyle: Does the chamber have a vent? If not, it is a design failure ... Almost every chamber I've seen has one to evacuate excess fog and balance pressures. You can drill a hole and put some pipes up to the roof, and it may serve you as well.

Hope you can solve your issues! Best regards!

A. Hi Kyle,

Well, the water layer at the bottom must be at least above the drain pipe level so it prevents fog leakage through it.

Try to maintain this valve closed and open it only to drain when the liquid is too high. We have this valve open but it goes right into a big equalization wastewater tank for treatment, so we don't really see any fog here in the lab.

You mustn't have any problem with this, because the pressure must be relieved through the roof venting. If it isn't, then you have some obstruction in it.

Hope you solve this issue! Regards,

A. There is NO way that you can certify any results from salt spray tests that were not run completely within the prescribed parameters. However as a rough rule of thumb that I find very useful, a chemical reaction will double in rate for every 10 degree Celsius increase in temperature. You can do the rest of the math for your specific situation.

A. Effect of unbalanced pH level on salt spray test

Do you have salt spray and CASS test cabinet in same room, possibility pH down in your collector water.

Make sure your pH meter is calibrated and working condition.
Check any acidic fumes entering into the salt spray room or that area.

A. When you see the term "shall" in a spec, rather than "should", it is compulsory rather than suggested, and something that an auditor will follow up on. Not only must you wait until your sample has cooled to that temperature, but it's a good idea to have a column on your log sheet showing the actual temperature of the sample at the time of pH analysis, because everyone knows an auditor's favorite phrase: "Show me where you recorded that". :)

A. Hi Moises,
The pH of your solution before it enters the salt spray chamber should be close to the desired 6.5 - 7.2 pH measured out of the collection sample (example the pH of the solution is in the 6 - 7.5 pH range) if your collection sample has a dramatically higher pH by more than one point from your starting solution there is likely a leak / contamination from the sample run offs.
The pH of the distilled water is not a big issue as long as you're using Hydrochloric acid and Sodium Hydroxide to balance the pH of the solution. It would be good practice to record the pH and salinity of the solution every time you refill and compare it to the collection sample to better understand how the composition is changing as it goes through the test.

Hello Mr. Montemayor,
The calculation for dilutions of solutions measured in Normality is the same as for any chemical solution measured in Molarity -- for monoprotic acids, these are equivalent values, and HCl is monoprotic so there's absolutely no way to get confused whilst doing it! :)
Here's a simple trick to set up your dilution equation:

Write out what you have, and what you are trying to get to, as a proportion, like this:

You have:    You want:

12.1 mol      .01  mol
________  =  _________
   1L           x L

First, MULTIPLY the diagonal values that contain the two known values.

1 x .01= .01

Next, DIVIDE by the diagonal value that is known.

.01 / 12.1 = .000826

To get your dilution factor, simply divide 1 by this result

1 / .000826 = 1210.6

Finally, verify your math:

12.1 / 1210.6= .009995 -Yup it works!

That means to make your .01N HCl from 12.1N HCl, you can put 1mL in 1210.6mL or 1.21L... or if you need a lot of it, you can put a litre in 1210.6L!

This may not be the way everyone would do a dilution calculation but I find that it is the absolute EASIEST way to remember.

Oh and MAKE SURE YOU USE ASTM GRADE OR BETTER DEIONIZED WATER!!! Or you'll end up with who-all knows what molarity by time dissolved stuff in the water has finished interacting with the acid!
FYI you can buy .01N pre mixed HCl at lab supply houses, not sure if you have Grainger up there, but it is a lot more convenient! And comes with a certificate of analysis to keep those auditors happy.

A. Hi brother Sergio!

You should rinse only when the test is over, as your client advised you. We check the status every 24 hours with just a general look at the parts, and as "white corrosion" is hard to tell a "GO/NO GO", we just see if there is any spot where the base metal shows (this is a "white corrosion indicator") and in painted surfaces there is no white corrosion in general, only "white clouds" from the salt spray.

This is only for daily inspection procedures, and you should validate your inspection procedures with your clients (as it says you should in B117). DIN EN ISO 9227 is another standard, very similar to ASTM B117, and just gives you another tools to measure your chamber aggressiveness.

I hope this clarifies your issue! Best of luck!

A. Hi Frederick,

I would look if your saturation column is working, because if the density goes up, seems your solution is evaporating and concentrating because the spraying air is not 100% saturated.

Hope it works for you!

Best regards,
Daniel