Corrosion around door frame

marvin4239 · Posted: Mon Sep 15, 2008 2:53 pm Post subject: Corrosion around door frame

While cleaning up my boat in preparation for a trip to NC for the gathering I noticed what appears to be corrosion around the door frame hinges, lock mechanism and some of the screws holding the frame in place. It hasn't breeched the surface of the paint but is definately bubbled up in those areas. I'm guessing it's a reaction to the dissimiliar metals stainless to aluminum. I tried to take a picture of it but couldn't get a good one. Has anyone else experienced this and what did you do?

Sea Wolf · Posted: Mon Sep 15, 2008 6:39 pm Post subject:

Marvin-

The simple answer is to replace whatever necessary to get the same metals in contact with each other, but it may not be that simple.

What are the hinges and lock made of? Stainless? (could be a cheap Chinese alloy that is not corrosion proof) Chromed Brass? Chromed zinc? Aluminum Alloy?

Can you tell by the hardness or magnetic properties?

What kind of screws are being used? (Mostly the same choices).

Getting the alloys matched would be the first step in the right direction.

Insulating the screws and hardware with zinc chromate paste is also a standard procedure used on sailboat masts where anodized aluminum alloy masts have stainless and other alloy hardware fastened to them with stainless, Monel, and aluminum rivets and other fasteners. (Makes for one big corrosion prone multi-cell battery, in one view!)

What to do about the corrosion already under the gel coat is another matter.

Dissolving the already formed corrosion salts could be a tricky matter, requiring some experimentation, unless someone with practical experience or a chemical engineer amongst us can step up to the plate here.

Read the following and see what you think:

What is a good solution for dissolving rust or corrosion?

I'd start with a Q-Tip and one not so obvious screw hole and see what I could do to dissolve and or neutralize the corrosion. Naval and aluminum jelly hold promised as does the Wal-Mart product.Be sure to flush with plenty of water and allow to dry out before re-assembling. Unfortunately, the bubbling may not go down. Once you get what you can cleaned out, reassemble with like metal screws and hardware (if possible), forcing zince chromate paste (available at marine hardware stores) into all spaces and contact points.

This is an "educated guess" on my behalf, I am not a NASA, U.S. Navy, or weapons industry metallurgical engineer. But I knew one once, God rest his wonderful soul!

Joe Teeth

marvin4239 · Posted: Mon Sep 15, 2008 7:43 pm Post subject:

Thanks for the advice Joe. As of yet the bubbling isn't that bad but I can only see it getting worse if I don't do something. I'm pretty sure the hinges and screws are stainless. I'll try to find some zinc chromate paste and treat the contact surfaces of the stainless to aluminum and see what happens. Perhaps that will stop the reaction between the metals. It might be a good idea for others to check thier door frames to see if they are developing a problem.

rogerar · Posted: Tue Sep 16, 2008 4:56 am Post subject:

Use TEF GEL to bed dissimilar metals, it's been around a long time and is specifically made for this, I just replaced all my window screws, and bedded them in TEF GEL.
Roger

Sea Wolf · Posted: Tue Sep 16, 2008 7:07 am Post subject:

marvin4239 · Posted: Tue Sep 16, 2008 8:32 am Post subject:

Thanks Joe and Roger I ordered a 1 oz tube of the Tef Gel from Jamestown and will try it. Again I'd urge others to check their hinges. My damage is only slightly cosmetic but in time I could see it easily corroding away the door frame.