Stainless, Cont

[Theis]

That web link is most interesting. In light of last year's discussions about replacing stays, the comments about 304 and 316 are most interesting. No one in my research last year even suggested that combining parts, some being 304 and others being 316 stainless would cause a problem. However it just made sense to me as a crotchety, critical, tube turnip. For example, combining a 304 clevis pin with a 316 shackle can cause corrosion. It also gives some substance against those that claim that SS only crystalizes, but seldom corrodes. So what are most SS screws/bolts made out of?

[marymandara]

Seems to me that stainless harware items--fasteners mainly--are worse and worse this way as more and more (if not almost all) of it comes from the third world and the orient. Plenty of recycled razor blade and who knows what else in there. Also, if the factory equipment that rolls the threads is not dedicated to only doing stainless, or very thoroughly cleaned between material runs (Hah!) there is a fair amount of ferrous particulate smooshed into the stainless parts.
Dave

[Theis]

The third world may be the problem, or the salvation. In former times US stainless was passed through an acid solition (nitric acid?) to get rid of any remaining iron particulate and bring the chrome to the surface. That process has become so environmentally sensitive that it is no longer being done here. The net result is that old stainless (and I am talking 50 year old stainless as well) is less likely to corrode than the new stuff.

The third world may be doing this extra process so that there is no iron particulate near the surface.

Does anyone know if there is any difference between WEST hardware and the stainless fasteners purchased at the local hardware store in this regard, or are stainless fasteners a generic commodity?

[Bill]

Commander Pete writes: I had a problem with rust forming around some of the screw holes in the stainless steel rubrail. I would get rust stains running down the side of the hull.

I took off the rubrails, sprayed the underside with corrosion inhibitor and rebedded them. Didn't completely solve the problem.

The I added mahogany rubrails to the boat and put the stainless rubrails on the outside of the wood. I attached the stainless rubrails using silicon bronze screws instead of stainless screws. So far so good.

I picked this tip up on the Pardey website.

http://www.landlpardey.com/Tips/Tips_1999_August.html

[Bill]

Ebb writes: Chromium in low carbon steel makes the iron stain less. Iron oxide is molecularly much larger than elemental iron & so makes an untidey flakey mess. Chromium oxide is similar in sixe to atomic,

Type 304 (18-8) s.s. has manganese, chromium and nikel in it (also carbon, silicon, phosphorus, sulfur.) 316 has molybdenum added to enhance the ability of chromium to form a tightly packed layer with its oxide to protect the alloy. This passive layer in 316 requires oxygen to make repairs to itself when clorides in the seawater attack the surface thru imperfections.

A wet buried s.s. screw lacks oxygen. Passivation on high end products is an attempt to clean the surface of unalloyed iron particles with nitric or citric acid. There isn't proof that it actually works. Then there is electropolishing to try even more to reduce crevices, craters and imperfections. But who would do it to a screw?

S.s. corrision begins in millionths of a millimeter pockets of sulphide where the chromium surface is compromised. The sulphides come from impurities in the ore and IMCO from the recycled junk in the foundry metal. (I would think, tho, that stainless production is highly controled and sophisticated because of its applications.) These miniscule craters draw chromiium from the alloy as it cools thereby making a steel that can stain more rather than less.

304 and 316 are very similar alloys (except for the molybdenum.) IMCO any corroion from galvanic action between the two couldn't happen. So it has to be the source of the stainless and what it is claimed to be, and how smooth its surface is.

Any buried s.s fastner exposed to constant seawater is going to get rusty. CHROMED BRONZE screws might be the way to go to attach the rubrail.
Has anybody tried the Loctite thread coating in this application? It might stave off replacement longer by keeping corrosion entirely away from the threads. contrary to what is stated above.

[ebb]

From the Pardey site mentioned by C'pete on another post, Larry mentions taking a small magnet with him when checking out new or unknown stainless stell and equipment. Smart.

True stainless is NONmagnetic.
If a magnet sticks to the s.s. it is b.s. Even if it says stainless, it is not.

[This statement was too simplistic for me, too! So I spent a bit of time on it, the subject is vast and my brain too small to be a metalurgist.
But here goes:

There are varying formulas for stainless steel but still have its composition within a specific range. All 300 s.s are variations of 304. 316 can be tweeked by adding or subtracting a percentage or two of chromium and/or nickel. Those two are responsible for keeping stainless carbon steel austenitic as possible. But reheating of the s.s. by forming or welding can cause ferrite to form. The chrome rich stable (passive) film is very thin. Heating to 500 degrees, eg, can cause the chrome to form chrome carbides from carbon present. This depletes the protective layer. The word austenitic refers to stainless in its true unaltered state.

The point is, you can take perfectly good stainless steel, machine it (screws, bolts) or weld it (hinged mast step) and you can bring the iron (ferrite) out of suspension, say, and you have a corrosion problem AND magnetic attraction.

So an engineer can specify cast 316 stainless and get less corrosion resistence than the rolled or bent formula, because of the heat changing the elements around. He should have said CF-8M to the foundry which has a higher chromium content and is non-magnetic and more corrosion resistent. Which is to say, a manufacturer of a marine stove can make have a big mistake in his assembled product where a part begins to rust even tho it is guaranteed to be 100% 316.
OK, that's more than the time allotted this subject. Carrying that magnet when buying is a very good idea!]


There should be a law!
It's better with bronze.

[c_amos]

Word to the wise, I purchased some 'stainless' piano hinges to replace the nickel plated bronze ones on the cockpit lockers. The nickel plating had worn off so when I repainted I bought shiny new stainless hinges at Home Depot.

They looked great, and the holes were on 2" centers just like the originals. I was very pleased.........

.... not sure if they were the wrong grade, but what I suspect was the HINGE was stainless, but the PIN was actually mild steel@!

After just a couple months they were a rusted mess, and could no longer be opened without bending the metal.

Cleaned the originals today, bare bronze will look better then the rusted mess I had (and open better too!)
Home improvement store piano hinges are not the way to go, FWIW.

[dasein668]

.... not sure if they were the wrong grade, but what I suspect was the HINGE was stainless, but the PIN was actually mild steel@!

That's the same reason I never buy the "cheap" stainless hose clamps at the West or similar (such as the IDEAL brand). They have low grade steel screws that corrode in about two minutes even though the band is stainless. Splurge on the nice AWAB all 316 clamps.

[ebb]

Bummer on those piano hinges. I got my all 316s from H.A. Guden. Including the 'pin'.

Dasein reminds me of an edjucational episode with hose clamps.
Spotted a deal in McMasterCarrs encyclopedic online catalog for a 316 hose clamp assortment. When I examined the cube shaped boxes that came in the toolbox (part of the deal) it was obvious that the clamps weren't 316 - they were 100% 300 series. So I sent them back. You know with a note and after calling central.

The warehouse sent them right back to me, same toolbox same clamps. The clamps were listed in the catalog as 316, so they were 316. So more phone calls. Got a holt of a human who believed me. And sent the clamps (and toolbox) BACK AGAIN. In the meantime I contacted the manufacturer/importer Breeze Marine and got on their website.

They have hose clamps made of 410, 305, and 316 in one group.
410 ss screw with a 300 series band saddle & housing, 305 screw with 300 series band saddle & housing, and an all 316 in another group.
304 band saddle & housing with a 305 screw, all 316 in yet another group.
100% 300 series s.s. in another group. And so on.

You got to watch that buzz word: s.s. McMasterCarr after some weeks (probably sending back and reordering their stock) sent me a toolbox containing the assortment of 316 hose clamps that had by now a recognizable part number on the little boxes.

Breeze also has those rounded band clamps (different part number) like the swede AWABs. I never did ask them who else retails their stuff. If I'd known Jamestown had swede AWABs I might have got them. BUT I am such a sucker for a deal!

The housing over the screw should be stamped with the maker's name and 316 stainless steel. Have to assume that all parts of the clamp are also 316, not just the housing.

I agree with those who say: that 304, found in many fittings and fixtures made for the marine trade has absolutely NO place on a salt water boat. If you must bury or forget a stainless fastening, fixture, wire rope or clamp, whatever, it MUST be 316 at the very least. If you have seacocks with hose attached, I would change out the existing clamps for new proven 316 the next time I could. Hose too. Cheap insurance.

[mrgnstrn]

One way to get around the problem of having hose clamps made of different grades of materials is to.................not use any.

At the Annapolis Boat Show, I got the niftiest tool, a hose clamp maker thing called the "Clamp-tite".

You take a piece of wire (your choice on grade) and basically wrap it around, this tool tensions it appropriately, and you give it a half twist, and done! Voile!

<snip>{I will try to post more info.}<snip>

http://198.63.56.18/index.html
for more info.

[ebb]

OK for the ingenious Clamp-tite!
Are you going to be able to use this tool on the seacock in the locker where you have barely enough room to hook the band of a hose clamp around, stick it in the housing and tighten with the nut driver? Can you use this jig in tite places?

Some tube because it is soft or thin is not going to be happy with wire, wanting a flat band, no matter what.

What wire is available that is right for wrapping and bending, eg is the monel wire you get for mousing good for clamping? Is there 316 wire? Is wire availability a problem?

How dependable is the wrap, how secure the finished twist? Can you trust the Clamptite system as you might an expensive 316 hose clamp? With curled edges? :rolleyes:

[mrgnstrn]

as for the "flat band" part, you can put lots of wraps on and effectively have a nice flat band (made up of a bunch of wires next to each other).

As for wire availability, I have a roll of SS316 for rigging stuff. I know that monel is also out there.

As for use in tight areas, the tool is shorter than the average screwdriver or nut driver that you would have to use to tighten the hose clamp.

I haven't actually put it to use, but it seems pretty secure. Unless you pry up the "tabs" (the two snipped ends locking the band tight). And the directions say to bend them down back into the tube as to not present a nice edge to accidentally grab onto.

I am planning on putting a clamp or two on this weekend, so I will report it's utility after that.

[ebb]

Practical Sailor never does real world testing. They now will even feature products they have not actually tested at all.

Give us a real time report, ok?

I don't kow how it works, thinking you have to winde the tool around and around to get the wraps, like a serving mallot used when parceling and serving galv wire - getting the tension right.
To make a band the tension on each row of wire would have to be pretty much the same. One wrap tighter than the others could do the cutting on the hose.

I really hope it works. Invention is the true spirit of the nation. Good tools and jigs bring true happiness. Yup, by golly. :D

[Mike Goodwin]

I have a friend that is an auto/boat mechanic and he uses one of these .
His is a Snap-on , he's a tool snob, but he has had one for at least 15 years .