MIL-STD-810F 509.4 and thoughts on salt water exposure
During a week of scuba diving off Roatan island in Honduras, I had first-hand experience of what salt water exposure can do to equipment. I took several underwater cameras with me for testing and used them on up to four daily dives to 85+ feet with each lasting an hour or more. I thoroughly rinsed off the equipment after each dive, but still found that salt accumulated under rubber coatings, inside screw holes, under screw heads and inside or under anything that allows water to go under or moisture to seep in. After I returned back home I soaked all equipment again in my bathtub and then cleaned each part and component. Without that, adjustment screws, hinges and joints could seize, and the equipment quickly deteriorate due to longer term corrosion.
I remember when Panasonic showed me the results of their Toughbook corrosion testing on an invitational tour of their facilities in Osaka back in 2002. 
Without special consideration of salt water and salt fog exposure, there could quickly be appalling damage as shown on the picture to the right (click on it for a larger version). Panasonic explained how they had been approached with requests for such testing, performed the salt water and salt fog tests, and were surprised to see the extent of the damage. They then systematically changed design and materials to ward off or minimize the effects of salt. This benefitted all subsequent Toughbooks, and also showed Panasonic how to develop special solutions for customers who use their products in environments where they are exposed to salt fog and water.
When you look at these pictures it becomes obvious that sealing alone is not enough when it comes to salt water exposure. Sealing standards only tell how well a product keeps dust and water out of the inside of the unit. They don’t tell what salt can do to components that lay outside of the sealing barriers. What can salt do when it gets under a keyboard? Inside a hinge? Underneath protective doors? The result can be ugly. Nothing can ever ward off salt entirely when a product is used in marine environments. Users need to keep computers away from excess exposure as much as possible, and equipment needs to be cleaned meticulously after any exposure. That means that cleaning must be possible in the first place, which means that places that are potentially expose to salt water and fog must be accessible. There are just a whole bunch of additional considerations.
This is why the famous MIL-STD-810F (Department of Defense Test Method Standard for Environmental Engineering Considerations and Laboratory Tests) document includes a 9-page section on Salt Fog testing.
MIL-STD-810F Method 509.4 describes testing methods to determine the effectiveness of protective coatings and finishes on materials for corrosion, electrical effect and physical effects. The tests can also determine the effects of salt deposits on the physical and electrical aspects of materiel. The product is exposed to salt fog mist from a 5% salt solution via atomizers at about 95 degrees Fahrenheit for a minimum of four alternating 24-hour periods, two wet and two dry. The product is then examined for salt deposits that can clog or bind components, electrical malfunction, and potential short and long-term impact of any observed corrosion.
The reason why I am writing this all down is because my return coincided with an announcement from GETAC that its impressive B300 rugged notebook had received Salt Fog certification. Here’s part of their press release:
LAKE FOREST, CA. ” “ September 2, 2008 ” “ GETAC Inc., a leading innovator and manufacturer of rugged computers that meet the demands of field-based applications, announced today that its B300 ruggedized notebook PC received full Salt Fog certification based on testing standards set by the Department of Defense (MIL-STD-810F ” “ 509.4). Salt Fog is a specialized test used to evaluate and determine the effectiveness of protective coatings and finishes on materials to repel salt corrosion and may also be applied to determine the effects of salt deposits on the physical and electrical aspects of materials. Adding the Salt Fog certification to an already robust and rugged notebook PC makes the GETAC B300 the ideal choice for military installations, marine applications such as the Coastguard and other industries where salt or salt air can impact equipment performance.
“Salt is one of the most aggressive chemical compounds in the world,’ said Jim Rimay, president, GETAC. “Salt will quickly corrode a computer’s exterior, impair vital electrical system functions through salt deposits and have a physical impact by restricting free movement of its mechanical components. The B300 addresses these issues with its Salt Fog certification and elevates it to an elite status among ruggedized computers for safe and uninterrupted operation in any location, especially in coastal regions of the world.’
We recently did a detailed hands-on test of the Getac B300 and found it to be a very impressive machine full of clever engineering and innovation. A combination of optical coatings and superbright backlight make the screen readable in the brightest sunlight, and amazing power conservation methods can extend battery life to a stunning 12 hours. It’s good to see that the company also invests in testing against one of the less-often mentioned environmental threats to mobile computers — salt fog exposure. While most specs include resistance to drops and vibration, salt fog/water exposure can destroy a piece of equipment just as surely. Once the corrosion is detected, it’s usually too late, so it’s nice to see Getac take proactive steps.
MIL-STD-810F, however, only describes testing methods, and not the criteria that determine passing tests. It would therefore be nice to know what Getac found during its tests, and what the company did to make the B300 as immune to salt fog damage as possible.