Aluminum Backplate/Galvanic corrosion

[vshearer]

Searched for any info on this and couldn't find it so I will ask. I am getting an aluminum BP to complement the current SS i dive (saltwater) and wondered if anyone ever has problems with electrolysis on these plates. Seems the Stainless STA and tank (as well as other dissimilar metal contact) might cause this to be an issue but since I don't see any posts about it I am wondering if this is so.

 

[Scubakevdm]

Searched for any info on this and couldn't find it so I will ask. I am getting an aluminum BP to complement the current SS i dive (saltwater) and wondered if anyone ever has problems with electrolysis on these plates. Seems the Stainless STA and tank (as well as other dissimilar metal contact) might cause this to be an issue but since I don't see any posts about it I am wondering if this is so.

I have one of the original Dive Rite AL plates... I'll post some pictures of the bolt holes.

 

[Scubakevdm]

Here you go. I put a newer, but still old ss dive Rite plate next to it so you can compare the holes. The aluminum plate has onle been in fresh water.

 

[vshearer]

Thanks for the photos, but the issue would really only occur is saltwater, which is what I am planning on using it for. I suppose the issue could be alleviated by not using a STA, using an aluminum STA, only using plastic sex screws, etc. but I am interested in others diving with AL plates in salt water and if they have this issue.

 

[dumpsterDiver]

My dive rite aluminum plate showed some obvious corrosion around the contact with the stainless bolts, after just 2 years. It might be a problem in another 8 years and then I would drill some new holes 3/4 of an inch away, I guess.

 

[Eric Sedletzky]

Thanks for the photos, but the issue would really only occur is saltwater, which is what I am planning on using it for. I suppose the issue could be alleviated by not using a STA, using an aluminum STA, only using plastic sex screws, etc. but I am interested in others diving with AL plates in salt water and if they have this issue.

I think you're getting way too concerned about it.
If the plate was living in salt water and you never took the STA off you might have a problem, but if you're disassembling and cleaning the rig each time in clean fresh water and drip drying it after I don't think you'll have any problem. A day of diving in Salt water isn't enough to get electrolosis started I don't think.

 

[vshearer]

My dive rite aluminum plate showed some obvious corrosion around the contact with the stainless bolts, after just 2 years. It might be a problem in another 8 years and then I would drill some new holes 3/4 of an inch away, I guess.

Thanks, that is exactly what I was wondering. As I am just now getting it I may swap it out for the Kydex model.

 

[do it easy]

Here you go. I put a newer, but still old ss dive Rite plate next to it so you can compare the holes. The aluminum plate has onle been in fresh water.

Is that actually corrosion or are the SS bolts just filing away the AL plate?

 

[james croft]

I have seen some galvanic corrosion occur on SS tank bands on aluminum cylinders. Usually this happened when there was not a rubber strip between the two. I have a SS STA and an aluminum
BP and use it primarily in fresh water so it is not an issue. I have wondered if it would be worthwhile to add a small zinc anode to SS tank bands before...Anybody tried this?

 

[ZzzKing]

I use nylon washers between the ss washer, the STA and the plate. That eliminates any chance for galvanic action as well as provides a compressible layer of material so the bolts don't back out.