O.T. stainless and galvanized metal

[RichardG]

Can you use stainless bolts in galvanized metal will they react with each other am redoing the boat trailer? Also have a pin hole in clutch cover on motorcycle will epoxy stand up to 250 degrees , this is a defect in the casting and a good chunk of change, would be nice if I could just epoxy it .
Thanks Richard

[Jim Stewart]

Around 15 years ago I built a BSA B50 (500 single) engine from boxes of parts from a junk yard. One problem was that three or four of the cylinder fins were broken off.

I built up the broken fins with JB weld, shaping them carefully after the epoxy had set for a couple of days. Worked beautifully, still looks good.

So in your case I'd apply JB weld from the inside, making sure it squeezes out through the pinhole. Make sure the inside surface is clean and sanded to give some grip for the epoxy.

-js

[danlb]

In my experience, you have a chance that it will work, but it's not 100%.

I've tried epoxy to fix cracks in aluminum and find that cast aluminum may have oil soaked into it that keeps the epoxy from bonding well.

Clean, clean, clean.


Dan

[cameron]

Can you use stainless bolts in galvanized metal will they react with each other am redoing the boat trailer? Also have a pin hole in clutch cover on motorcycle will epoxy stand up to 250 degrees , this is a defect in the casting and a good chunk of change, would be nice if I could just epoxy it .
Thanks Richard

The SS is strongly electro-negative relative to the zinc coating, so the galvanizing will provide protection for the bolts. The converse of that is the SS will hasten the corrosion of the zinc.

If the galvanized metal is the frame of the trailer, as I'm thinking it probably is, there's a lot greater area of zinc than of SS. The increased rate of corrosion of the zinc in that case will probably be fairly minor and probably acceptable.

Even so, it's probably worthwhile to provide some insulation of the two metals from each other. Some will recommend an anti-seize compound. I believe you can't do better than coating the bolts, nuts and threads liberally with pine tar before installation.

Working on a car, I never put an undercarriage or other exposed fastener back in place without pine tar. Ten years of winter driving on salted roads later, the fastener is easily broken loose, and when you remove it, you get that lovely smell of the pine tar, still in place and still doing it's job.

[754]

How big a hole ? Can you run a drill bit thru it, get it round. Then make a small aluminum pin with a head on one end like a rivet..about a thou bigger than the hole, press it in from the back with loctite.
Then dress off the part that sticks out on the outside.

[johansen]

The SS is strongly electro-negative relative to the zinc coating, so the galvanizing will provide protection for the bolts. The converse of that is the SS will hasten the corrosion of the zinc.

If the galvanized metal is the frame of the trailer, as I'm thinking it probably is, there's a lot greater area of zinc than of SS. The increased rate of corrosion of the zinc in that case will probably be fairly minor and probably acceptable.

Even so, it's probably worthwhile to provide some insulation of the two metals from each other. Some will recommend an anti-seize compound. I believe you can't do better than coating the bolts, nuts and threads liberally with pine tar before installation.

Working on a car, I never put an undercarriage or other exposed fastener back in place without pine tar. Ten years of winter driving on salted roads later, the fastener is easily broken loose, and when you remove it, you get that lovely smell of the pine tar, still in place and still doing it's job.

interesting idea with the pine tar as regarding rust prevention, but there are few insulators that will hold up to the 30,000+ psi pressures under the nut, and under the head of the bolt that will successfully prevent metal on metal contact with regard to electrolytic action. anodized aluminum washers (probably two of them required) might do the trick. of course you can use a steel washer to spread the load and plastic under it, you still need a sleeve around the bolt, or enough clamp load to prevent the bolt from handling the sheer stress, which will cut through any coating on the bolt. of course, you could sleeve the bolt with plastic too.

[RichR]

interesting idea with the pine tar as regarding rust prevention, but there are few insulators that will hold up to the 30,000+ psi pressures under the nut, and under the head of the bolt that will successfully prevent metal on metal contact with regard to electrolytic action. anodized aluminum washers (probably two of them required) might do the trick. of course you can use a steel washer to spread the load and plastic under it, you still need a sleeve around the bolt, or enough clamp load to prevent the bolt from handling the sheer stress, which will cut through any coating on the bolt. of course, you could sleeve the bolt with plastic too.

Who says you need an insulator? If you can seal the area to keep out anything that would behave like an electrolyte that should inhibit
any corrosion, shouldn't it?

[J Tiers]

If I read this right, it is a BOAT TRAILER, and not a boat.

Since it will be in water just sometimes, and will dry out in between, all electrolytic corrosion will be LOCAL, and also will be intermittent. NOT like a boat hull, etc.

I assume the trailer is made so it drains, and does not hold water inside a box beam etc. Therefore it will dry out and rarely be wet for any extended time. aside from standard outside weathering. When you pull the boat out and drive home it should be thoroughly dry from the trip, barring rain.

I don;t think it will be in any way more of a problem than ordinary steel would be. Use never-seez on the threads and faying surfaces, and you will likely get rid of the trailer before you notice a thing..

[Forrest Addy]

Stainless fasteners against a galvanized frame? Long term salt water immersion splash zones, bad idea.

A boat trailer is dipped infrequently. I don't think stainless fasteners against a galvanized frame will cause a initiate corrosion site unless the salt water pools or some reason.

If it's fresh water service, I don't think there will be a problem regardless.

Why not use galvanized fasteners? They're about as expensive as stainless but the dissimilar metals problem doesn't arise, especially if you spoof every fastener site and joint margin with Galv-a-Con.

[RichardG]

Thanks for all the advise it is a roller bunk boat trailer I guess I will just stick with galvanized bolts One of the 5/8 " bolts sheared off on the front roller set improvised and got it home it had grade 5 bolts switched to grade 8 but while I was working on it I noticed that a lot of the bolts on the rear rollers were in poor shape will replace them to. The pin hole in the casting is on a 2014 ktm 1190 the clutch casting takes a act of god to remove so was trying to find a better way to fix it . Its right where a strenthing fin is right in the coroner you can't see it but it weeps oil on to the hot pipe it did not start weeping to about 4 months and I finally found where its coming from.
Richard