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Old 06-08-2018, 01:23 PM
StressedOut StressedOut is offline
Join Date: Jun 2017
Location: Fullerton, CA
Posts: 130
Default Alodine on 4130 Steel - Problem?

I thought I was being so careful and thinking ahead. I wanted to protect the fastener holes on the hinge brackets on the horizontal stabilizer from corrosion by applying Alodine on the bearing surface. I took the brackets, thinking they were aluminum, and immersed them in Alodine to cover the bearing surface. These brackets, at least on the RV-14, are powder coated.

It was later in my build I realized that the hinge brackets were made of 4130 steel and not aluminum. I suppose the powder coating should have been my clue.

Now I'm concerned I may have compromised the steel with the Alodine. I've heard some rumblings about embrittlement of the steel with exposure to Alodine. I know of hydrogen embrittlement of steel, but I don't know if this is related. Since this is a very critical part in that failure of the part = loss of the airplane I don't want to take any chances.

Does anybody know about this? Can someone point me to some information? I've tried a Google search and nothing comes up specifically about Alodine and steel.

I can deal with replacing the hinge brackets on the horizontal stabilizer right now since I haven't yet riveted the rear spar assembly into the skin. I planned to do that on Sunday. I'll have to drill the rivets out, but that's no big deal at this stage of the build.
Art Jackson
RV-14A Kit#140433, N393AJ Reserved
Completed: Vertical Stab/Horizontal Stab
Scrapped: Rudder
Working on: Empennage (Elevator)
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Old 06-08-2018, 02:13 PM
BMC_Dave BMC_Dave is online now
Join Date: Mar 2017
Location: Seattle, WA
Posts: 256

Chromate conversion coating (Alodine) will have no effect on bare steel. It is apparently used on steel parts that have either been zinc or phosphate coated.

There is no risk of hydrogen embrittlement with chromate conversion coatings.
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Old 06-08-2018, 04:03 PM
Nedimbek's Avatar
Nedimbek Nedimbek is offline
Join Date: Nov 2015
Location: Calgary, Alberta
Posts: 78

Hydrogen enbrittlement is a by product of electroplating. It has nothing to do with alodine chemicals.
Nedim Bek
Starting soon.
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