Uh Oh - Never Say Dye

[Roger Long]

I found this suspicious line on my prop shaft. Rubbing the area with a Scotchbrite pad didn't seem to fade or remove it a bit. It's smooth to the touch but it looks a lot like a crevice corrosion crack.

I'm having the yard dye test it. I hope I haven't answered the question in my earlier post, What else am I not thinking about?

 

[caguy]

I found this suspicious line on my prop shaft. Rubbing the area with a Scotchbrite pad didn't seem to fade or remove it a bit. It's smooth to the touch but it looks a lot like a crevice corrosion crack.
I'm having the yard dye test it. I hope I haven't answered the question in my earlier post, What else am I not thinking about?

If its off the boat you might want to have it magnafluxed.

 

[Roger Long]

The service manager, myself, and the rigger who did the dye test were all equally surprised not to find a crack. However, only one of us was significantly relieved.

I really don't want to have to take that shaft out of the boat this spring.

It's weird. None of us have seen anything quite like it. It's either a flaw in the original metal or the beginning of crevice corrosion that hasn't progressed to a crack. I'll keep an eye on it each haul out.

 

[jibes138]

It looks like it goes all around the circumference. Maybe you wrapped a lobster pot float and line and it scratched the stainless? I've seen flaws in bar stock where an inclusion gets drawn out as they cold roll or draw the bar. These flaws usually go along the axis of the bar not circumferentially. Crevice corrosion is usually occuring in the absence of water flow where oxygen is depleted, like in the root of a screw thread. I actually had a bolt fail that was used for the lower shroud of a Catalina 25 once due to crevice corrosion. A deck leak around the fitting resulted in crevice corrosion at the root of the thread. Amazing how little good metal was holding it together when it failed.