Need to buy or design/build salt spray chamber

A. Hi, Mike.

I'd start by examining the newest salt spray cabinets from the existing suppliers and see in what ways, if any, they seem deficient to you. Then I would do a patent search because there are certain accessories or approaches you are prohibited from offering. Then I would check the ASTM corrosion tests to see what kind of specifications the cabinets you wish to design must meet.

I think you'll find letter 7583 interesting as the inquirer asked what factors are important in choosing a salt fog cabinet and several readers offered their answers. Good luck!

A. First of all, take a look at what is already commercially available. There are a few major companies that already do very well in this market. You will have to have some sort of advantage over existing cabinets to convince people to buy from you. If you are not already intimately familiar with salt spray testing, I don't see how you could compete.

The cabinet must fully comply with ASTM B117. Good cabinets will also have the capability to run humidity testing, CASS testing, and perhaps even Kesternich testing. A top-of-the-line chamber must have controllable temperature, fog rates, and relative humidity. It should be able to do cyclic tests and be programmable for custom cyclic testing.

Make sure you understand what you are getting into before you invest a lot of money, time, and effort.

Good luck!

A. Hi, Mallika. I'd certainly start with ASTM B117. And I'd suggest making it of fiberglass rather than steel. Best of luck.

A. Hi, Ilya. If you just wish to accelerate the corrosion, with no standards to meet, just pour wet salt on the boards, leave them in the sun, and spritz when they get dry.

But if you seek repeatability, yet don't wish to buy a salt fog chamber, you might do a search for "CAMRI testing". This is a highly repeatable accelerated corrosion test that can be done with very little investment, and has been used by very reputable organizations including the International Zinc Association. Good luck.

A. Attached is a pic of a DIY chamber I built to test supplier hardware used on high end high performance windows and doors. Like most of your responders suggested I went to ASTM B117 to put together requirements for establishing the design intent.

Much of these products I test are used on or close to ocean front environment. Also I test samples from in-house painting and vinyl film laminating.

This unit which we invested about $500.00 has been operating about 6 months. In that time it has paid for itself about 10-fold. I can give details if requested.

Most suppliers I deal with are eager to make changes to correct issues I have found in their products.

I would be happy to share details of design and parts used.

A. I will work up the specs - mostly hand drawn and a parts list.
I'm only interested in refinements discovered by other builders and users. E.g., you may choose to use different materials and circuits that are a more efficient design than mine.

I will include some pics of tests results That caused actual changes in design and/or metals used in the assembly.

You should see something by end of next week.

Thanks for your interest

A. Attached you should find parts lists and schematics of the chamber and pictures of the critical parts.

Schematic
Sketch
End view

Air brush
Air solenoid
Air source
Aspirator
Aspirator hook-up
Auxiliary outlets
Collar and water seal
Control panel
Hanging rack
Relay, breaker, solenoid
Rubbermaid cart
Tank ports
Tower with service loop

Salt Fog parts "partial list"

Digital Hydrometer 3.50 E bay
420 NM UV Light 30.00 E bay
110VAC digital prog. timer 7.25 E bay
100W silicone Pad heater 27.00 E bay
SS 8 Qtr. Pressure Cooker 50.00 E bay
Single burn hot plate 19.00 E bay
Thermostat with relay 14.00 E bay
PVC pie & caps 12.00 Lowes
Drain hose 2.50 Lowes
Drain port 3.50 Lowes
Aspirator ( air brush) 10.00 Harbor fright
PVC column and Base 12.00 Lowes
Glass 65.00 Tecnoglass
Plexi - top 50.00 Lowes
Control box and relays 100.00
Re. Glass - An aquarium will work - just be careful with heater pad (if used) e.g., thermal shock may crack the glass.

These parts were collected over a period of about 6 months. Some items purchased did not work well and replaced with the parts you see in this list. Look over the schematic and start shopping. Only the thermostat and timer from the control box are on this list. I'm sure you could get the rest of the relays and breakers on eBay or a surplus house of your choice.

Good luck and let me know how you've improved this design.

Thanks
TW

Great work Tom, and incredibly generous of you. Thanks for sharing.

Regards,

A. Hi Abhay. I would start by obtaining a copy of ASTM B117 or ISO 9227 since I'd assume that you would want the results of your 5% salt spray test to be similar to the results that others get when they conduct 5% salt spray tests, and you'll want to know what you have to do for your results to have validity in that regard.

After that, you might follow Tom West's explicit directions, or ask highly specific questions about them. Good luck.

Regards,

A. Hi Cody. Tom included an electrical schematic as his first link. Good luck.

Regards,

A. Hi Andrew,

In general, the salt solution goes by gravity to a middle tank (this tank with a floating valve) with the same level as an inner tank, this with the nozzle. This system is feed with water-saturated air, and it sucks (by venturi effect) the water from the inner tank into the nozzle and therefore into the chamber.

There are many schematics of this, but every nozzle I have seen for this type of chambers works the way I described.

Hope it helps!

Hi Andrew!

I was sure that what I was trying to explain was very complex to say with words only.

I drew a very schematic view of my chamber, so you can see how it works...

Saturated air is injected into an ejector, which sucks the salt water into the chamber. This ejector has this shape (I tried to draw it as I remember it, as I can't take it from the chamber without interrupting all our assays) that allows liquid to go up because of the low pressure in the upper part, and you can make the volume of this chamber (between the cap and the cone) higher or lower by screwing or unscrewing the cap, this makes bigger or smaller drops in the ejected spray.

Hope this helps you in your project! Best of luck!

A. Hi Nejc,

I don't fully understand your questions, because we don't have any burners in our chamber, and I don't know any gas fueled salt spray chamber. So, I will answer the things I understood of your questions:

1- The chamber is warmed by two ways:
a) The saturated air is at 40 °C when it enters the ejector. It cools a little when it comes out the ejector, but heat enters the chamber anyway.
b) There is another chamber full of deionized water under the salt spray chamber. This chamber is heated by an electric heater with a thermostat. It heats up to 60 °C this chamber, and by contact it warms the chamber to a comfortable 35 °C. Keeping some salt water at the bottom of the salt spray chamber keeps it regulated well enough between 34.5-35.5 °C.

2- The chamber is not well isolated, It's only plastic. It doesn't have to be very isolated to allow over-temperature to wear off when it comes to that, and you only need a small heater to keep it working day and night at optimal temperature.

Hope it helps!

Best regards,