The Editor says: As underwater photography gear becomes more and more affordable (though the Editor still can't quite afford it!), many divers are adding camera equipment to their kit and bringing it underwater. Beyond rinsing gear in fresh water after surfacing and replacing O-rings regularly, seized screws caused by salt buildup are a headache that constantly plagues underwater photographers. Let's take a look at what the professional Boss Hao from 水舍水中攝影器材 has shared about the causes and prevention of the seized-screw syndrome! (Full article reprinted from the 水舍水中攝影器材 Facebook page)
Most underwater photography equipment today is made primarily from aluminum alloy as the main metal material. However, aluminum alloy is highly susceptible to corrosion by seawater, so during manufacturing, an anodizing layer is applied to the exterior of the aluminum alloy — which also changes its surface color (though silver-toned anodizing is available as well). Think of the anodized layer as a protective shield for the aluminum alloy, preventing the corrosion-prone metal from coming into direct contact with seawater. Because aluminum alloy is lightweight and highly versatile in fabrication, it has become the dominant material used in underwater photography equipment today.
Why Do Screws Get Salt-Seized?
To hold the various components together, stainless steel screws are almost universally used as fasteners. But you've probably noticed that after using your gear for a while, the threads of screws locked into aluminum alloy become coated with a white crystalline powder — commonly referred to as salt seizure. However, this white powder is not actually salt crystals; it consists of trace metals and minerals found in seawater. But why do these crystals only form on the stainless steel screws?
Just two screws, and look at how much crystal buildup they collected — removing these two screws nearly snapped them off entirely!
Most underwater photography equipment runs on electricity, especially high-powered strobes and Flash Lights. When electrical devices operate, they generate static electricity. On land, our electronics are protected by grounding wires that dissipate static charges — but there's no equivalent solution for underwater use. While the aluminum alloy body acts as an insulating shell thanks to its anodized coating, the stainless steel screws have no such insulating treatment. As a result of the galvanic potential difference between the metals and the electrolytic reaction that follows, mineral crystals begin to form on the stainless steel screws at the point where they meet the aluminum alloy. Over time, these crystals fill the entire screw thread and begin to degrade the anodized layer on the surrounding aluminum alloy. As the crystals accumulate and pack every gap, the screw eventually becomes completely seized!
A screw that was never lubricated — the threads are packed with crystals, almost completely fused to the aluminum alloy ball mount.
If the anodizing on an aluminum alloy underwater housing is poorly applied, localized corrosion can also occur. Experienced users know that when tiny bubbles appear on the housing body, it's a sign the aluminum alloy is being corroded!
>>Wake up — the boring part is over!<<
How Do You Prevent Screw Crystal Buildup?
The solution is to apply a barrier material between the stainless steel screw and the aluminum alloy. The most common options are silicone oil and waterproof grease. If you choose silicone oil, go for the white variety — white silicone oil currently offers better waterproofing and is less likely to be washed away by water. The other option is waterproof grease, which can be purchased at a hardware store — look for automotive or marine-grade grease. Different formulations yield different results, but in my experience, red or blue waterproof grease is almost always a safe bet. I'd advise against the tan/khaki-colored variety — that type of grease tends to emulsify after prolonged exposure to seawater, meaning it gradually becomes sticky and can even harden, which in severe cases can make screws just as difficult to remove!
In my experience with red and blue waterproof grease, after six months of seawater exposure there is no hardening or stickiness — only a slight darkening of color or a minor reduction in grease volume. It provides up to a year of protection. On average, disassemble everything once a year, wipe off the old grease, and apply a fresh coat — and your screws should never get seized in your underwater photography equipment again!
Of course, if you'd rather not deal with all that hassle, you're always welcome to purchase directly from 水舍水中攝影器材 — we lubricate all the screws for you during assembly!
If you can swap in new screws, that's the easy route — but you can also scrape off the crystals with a blade, and pairing that with an ultrasonic cleaner makes the job even more efficient.
Just look at all that white powder covering the table~~~
Applying waterproof grease to the screws.
And just like that, you can say goodbye to seized screws on your underwater photography equipment.
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