Hardware and Inserts, Dissimilar Metals

brapperdoodle

brapperdoodle

Location
Asheville, NC
Ive been trying to understand and research how galvanic corrosion happens and what I can do to prevent it. I noticed that the stock Superjet inserts are brass, and use stainless steel hardware. Some of the inserts I had to use for my build are 316 Stainless Rotaloc inserts and my question is this, Should I consider using a brass socket head screw for the stainless inserts? Or, should I just be using 316 stainless hardware in the 316 stainless inserts with marine grade anti-seize (no metal, graphite based)? Im just curious because im about to order some hardware from McMaster and they have what I need in stainless or brass. So, any opinions would be appreciated!
 
S

Storbeck

Location
Minnesota
It's a very good question. I don't know the answer, I do know that the stainless screws everybody likes to use in the billet aluminum that everybody likes to use are not a great combination for a guy that pieces together used stuff because he's on a budget (me). I've spent a lot of time getting stainless hardware out of billet parts that I got a "deal" on.

I have been using the McMaster "zinc aluminum" coated steel hardware for the stuff I've been putting together. I like them because that coating is very corrosion resistant, it's relatively cheap, and the steel parts stick to a magnet so I can get them out of the bottom of my hull when I drop them, plus the regular steel hardware is much stronger than stainless, not really a big concern because our fasteners aren't very highly stressed, but it does give you a little better fighting chance if something does get stubborn.

I've had zero issues with corrosion so far but I've only been using this stuff for a couple of years and I'm all fresh water, so it's not a very good test of corrosion resistance.

Your mileage may vary.

I've had stainless seized in stainless and stainless seized in aluminum. The factory bronze (brass maybe, not sure) inserts have never given me any trouble but I think the factory fasteners are plated steel not stainless, not super sure I'm always dealing with used stuff of questionable history. I know the factory fasteners on the motor are not stainless they're plated steel.
 
Christian_83

Christian_83

Xscream
Location
Denmark
I dont think you will ever have an issue wil galvanic corrosion, if you are "in a glass" hull. If its a carbon, its a whole diffrent story.
If would however, try to go for alu or brass inserts. Im not the biggest fan of stainless to stainless bolting in a jetski.
 
SteveC

SteveC

Location
West MI
FYI, in case not already aware: stainless steel will gall against itself, so anytime you put stainless to stainless, you run the risk of a mechanical lock that you realistically can't recover from without drilling/machining. It's possible in some case, but do NOT count on it. So, the point is that if you mate stainless to stainless, you want to put a thin and complete layer of some type of barrier/lube in place. Loctite works pretty decent there, believe it or not. If it's not something that you want loctited, a high pressure bearing grease works great, according to people who do this type of stuff for a living. ( edit: a metal-appropriate anti-seize is really the right answer, but having to have a specific tube of anti-seize for the metals at hand was more of a hassle [ even figuring out the right one to use ] and I don't think enough water will get in there to wash the grease out before I take it apart again).

Regarding galvanic corrosion: not being in salt water is a huge help. I think a lot of the trash stuff that's available out there came from salt water skis. If you ride fresh water, and keep the ski out of the water most of the time, and remove the hood to vent moisture when not riding... I would be surprised to see extensive galvanic corrosion (no one I personally know has experienced it, but I'm sure someone will chime in saying they have). Rust, on the other hand, just needs some water and oxygen. I used some non-stainless (zync plated) washers at one point, and because of being installed/removed more than one, the plating was imperfect, and it rusted. Not enough to cause any big problems, but it did. The same exact setup but with stainless washers did not rust, as expected.

TL;DR: I'm a fan of stainless. Just use anti-seize type lube or loctite on all threaded surfaces that will mate stainless-to-stainless.
 
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fastgtfairlane

fastgtfairlane

Location
Charlotte, NC
Loctite blue is a great thread sealer. Also “marine” grade anti seize works well too as the marine grade does not have any copper in it and works with salt water. I’ve not really seen any issues with corrosion until you go in the salt water and then it seems nothing stops corrosion in salt water. I always coat my engine bay and cables and such with wd40 before and after going to the saltwater
 
brapperdoodle

brapperdoodle

Location
Asheville, NC
I typically use a silicone spray on my ski pre and post surf riding, as well as washing it down thoroughly with "Salt-Away". I always store my ski with the hood removed also. Im not the person that rides my chit hard and puts it away wet, im pretty good about maintenance and keep stuff in tip top condition. I just want to know if I go to pull some bolts out in a few years, they'll come out! haha I have also had great success using the Loctite 572 on pretty much anything. But on stainless to stainless, I believe it is proper to use anti-seize of a graphite base.
 
M

mikesx

brapperdoodle said:
Ive been trying to understand and research how galvanic corrosion happens and what I can do to prevent it. I noticed that the stock Superjet inserts are brass, and use stainless steel hardware. Some of the inserts I had to use for my build are 316 Stainless Rotaloc inserts and my question is this, Should I consider using a brass socket head screw for the stainless inserts? Or, should I just be using 316 stainless hardware in the 316 stainless inserts with marine grade anti-seize (no metal, graphite based)? Im just curious because im about to order some hardware from McMaster and they have what I need in stainless or brass. So, any opinions would be appreciated!
Click to expand...
I wouldn’t think the problem is galvanic corrosion, its more of a galling situation. Stainless fasteners in stainless inserts are fine as long as you practice proper thread “etiquette “. Clean straight threads are priority one. Get in the habit of running a rethreader, (NOT A TAP, taps are for cutting ) in the threads, and a rethreading die on the threads. Use an air chuck to blow em out. Never use stainless in stainless fasteners to “pull“ a part together. The beginning threads distort in relation to the deeper threads almost guaranteeing a gall. When your fully seated and you final torque you are equally loading the entire thread. Neversieze is a MUST !!! I only use Nickle Never Sieze, dark gray , 3 times the cost of the tin man silver regular neversieze. Some guys use Loctite 567, a white teflon-like paste, I‘ll only use that on stainless pipe thread, though I've seen it used on bolts. Cleanliness matters, the smallest amount of grit is sure to gall your threads. My experience is once properly conditioned and maintained stainless in stainless is fine. I have 316 bolts in 316 inserts, and I have 304 bolts in 316 inserts, no problems with dissimilar metals, provided they are clean, straight, and neversiezed.
 
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kevbo

kevbo

Location
dfw
Corrosion problems are mostly aluminum close to any steel or carbon fiber part. Of course, stainless on stainless will gall without clean threads and lube. I have had great luck over the years with any Teflon thread sealant on PWC fasteners. Use it on threads and bolt heads, it seals out water.
 
brapperdoodle

brapperdoodle

Location
Asheville, NC
I did say galvanic corrosion, but I was also grouping in galling on SS to SS connections. I know galvanic corrosion and galling are 2 different things. My understanding is that on a Stainless bolt threading into Brass insert or Aluminum threads, you should be using a Blue thread locking compound OR a Teflon thread sealant/Loctite 572. Both of those will seal the threads and not allow water inside to begin the galvanic corrosion process. I know there are other things you can use on the threads (grease, anti-seize) but from what I have researched, a locker or sealant would be the ideal combination for that application. Now, on a SS to SS application, galling is the issue. Mike pointed out some great ways to prevent this and also using an anti-seize to lubricate and help the threads stay cool while installing. NEVER use a high speed install tool (drill or impact) on SS to SS. This will create high friction on the thread contact surface and will greatly increase the risk of galling. You want a slow and smooth install with lubrication, and like Mike said, no high tension "pull together parts" threading. That again will create high friction on the thread contact. As far as lubrication goes, I researched that using a non-metal anti-seize is ideal for SS to SS because you are not adding another dissimilar metal to the mix. I think any anti-seize would work fine but if you are OCD like me, a graphite based anti-seize is preferred.

But 1 last question, do I get the Brass bolts or Stainless?? haha They are almost exactly the same price! Im sure either would work fine, but I figured I would ask just to make conversation :cool:
 
M

mikesx

brapperdoodle said:
I did say galvanic corrosion, but I was also grouping in galling on SS to SS connections. I know galvanic corrosion and galling are 2 different things. My understanding is that on a Stainless bolt threading into Brass insert or Aluminum threads, you should be using a Blue thread locking compound OR a Teflon thread sealant/Loctite 572. Both of those will seal the threads and not allow water inside to begin the galvanic corrosion process. I know there are other things you can use on the threads (grease, anti-seize) but from what I have researched, a locker or sealant would be the ideal combination for that application. Now, on a SS to SS application, galling is the issue. Mike pointed out some great ways to prevent this and also using an anti-seize to lubricate and help the threads stay cool while installing. NEVER use a high speed install tool (drill or impact) on SS to SS. This will create high friction on the thread contact surface and will greatly increase the risk of galling. You want a slow and smooth install with lubrication, and like Mike said, no high tension "pull together parts" threading. That again will create high friction on the thread contact. As far as lubrication goes, I researched that using a non-metal anti-seize is ideal for SS to SS because you are not adding another dissimilar metal to the mix. I think any anti-seize would work fine but if you are OCD like me, a graphite based anti-seize is preferred.

But 1 last question, do I get the Brass bolts or Stainless?? haha They are almost exactly the same price! Im sure either would work fine, but I figured I would ask just to make conversation :cool:
Click to expand...
Stainless FTW! Just beware of I gottagoforarideitus.
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
Yup, blue loctite is your best friend for keeping threads sealed and secured. I've cleaned a boat load of bolts and reinstalled using blue, they always come out cleanly and never build up any form of mineral deposits. I ride in freshwater, many times I have encountered the white calcium buildup from hardwater, but also have seen multiple times where electrolysis will also corrode and leave the white deposits behind. Because there's always some form of electrical current in everything due to electron movement through the water, generation of current from the ski, other boats etc, if it's in contact with water it will always be exposed to a level of electrolysis. This is why you see that little alloy block on the lower unit of outboards and inside the waterjacket of the Yamaha motors. It's called a sacrificial annode. It's a softer and more electrically attractive alloy to help absorb the brunt of the electrolysis going on. I've dismantled many ski pumps that had white corrosion between the pump bolts and the bronze inserts, I had to do a very light pump boring once too on a Blaster that had a few swollen spots binding the impeller, everything around here is strictly freshwater and corrosion/electrolysis still happens. If it can get water exposure, it'll get electrolysis exposure guaranteed.
 
Freakie

Freakie

Location
Cape Town
I find myself on the wrong side of this thread on both the galvanic corrosion side and the SS galling side.... I ride salt water 90 %

My SuperFreak carbon hull has eaten my aluminium water lines under the tray a few years ago ....replaced with stainless a while ago....its now eating my alumunium reduction nozzles and I am on my second one already..the aluminium just rots away around the bolt holes until it breaks...even my aluminium pump insert is slowly getting eaten....I guess it is what is galvanic corrosion.....on the SS galling issue.....I had my impeller get locked onto my shaft that nothing could remove it....I used copper slip during assembly.....ended up losing the impeller and the shaft and about 500 USD in order to save the torrent 148 pump....just rebuilt another one with a new impeller and a new shaft.....used copper slip again.......have I MESSED IT UP again.....what should I use to prevent galling....HELP
 
Sparkplug

Sparkplug

Location
Red Bluff CA
Grease. Marine grade grease. The thick blue stuff. It's the only grease you need go use on anything that costs less than 1000000 dollars or doesnt go on the space shuttle. It will prevent corrosion and galling across a wide range of materials. For a very long period of time.

Like mentioned. Loc tite is spec generally because of its ability to lube and protect threads. Thats why blue is called for on most assemblies. But grease does just as good of a job. And you only need 1 tube to do every part on the ski. Not tiny little bottles of blue crap that drips everywhere. But to each their own.

Carbon sucks. It's gonna eat anything metal you put on it. Especially if you are in a salty environment.

Sent from my SM-G970U using Tapatalk
 
88kawi5fiddy

88kawi5fiddy

pew pew lazers!
Location
So Utah
grease, loctite.

ugga dugga it in without any lube, that way it cant ever become loose.

Christian_83 said:
I dont think you will ever have an issue wil galvanic corrosion, if you are "in a glass" hull. If its a carbon, its a whole diffrent story.
If would however, try to go for alu or brass inserts. Im not the biggest fan of stainless to stainless bolting in a jetski.
Click to expand...
the hull material being glass will have no change in effect from galvanic corrosion, meaning it will still occur.

carbon is a cathodic material, and aluminum is anodic. that is why aluminum gets eaten up by it.

see chart below:
 

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M

mikesx

Freakie said:
I find myself on the wrong side of this thread on both the galvanic corrosion side and the SS galling side.... I ride salt water 90 %

My SuperFreak carbon hull has eaten my aluminium water lines under the tray a few years ago ....replaced with stainless a while ago....its now eating my alumunium reduction nozzles and I am on my second one already..the aluminium just rots away around the bolt holes until it breaks...even my aluminium pump insert is slowly getting eaten....I guess it is what is galvanic corrosion.....on the SS galling issue.....I had my impeller get locked onto my shaft that nothing could remove it....I used copper slip during assembly.....ended up losing the impeller and the shaft and about 500 USD in order to save the torrent 148 pump....just rebuilt another one with a new impeller and a new shaft.....used copper slip again.......have I MESSED IT UP again.....what should I use to prevent galling....HELP
Click to expand...
I ride salty (brackish) and saltier (ocean) 100% of the time, carbon hulls, and this works best for me. I slop this stuff on ss imp and shafts when I assemble. I'd stay away from anything with copper or aluminum in it.
DSC06230.JPG
 
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