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Old 06-08-2018, 02:23 PM
StressedOut StressedOut is offline
 
Join Date: Jun 2017
Location: Fullerton, CA
Posts: 122
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.
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RV-14A Kit#140433, N393AJ Reserved
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  #2  
Old 06-08-2018, 03:13 PM
BMC_Dave BMC_Dave is offline
 
Join Date: Mar 2017
Location: Seattle, WA
Posts: 208
Default

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.

https://en.wikipedia.org/wiki/Chroma...ersion_coating

There is no risk of hydrogen embrittlement with chromate conversion coatings.
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  #3  
Old 06-08-2018, 05:03 PM
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Nedimbek Nedimbek is offline
 
Join Date: Nov 2015
Location: Calgary, Alberta
Posts: 75
Default

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