Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

[Cheechako]

yeah... good point. I assume the mill grinding is done with abrasive, but as a note to the OP... dont use anything that has been used previously on steel. Grinding a 2" wide SS bar is going to use many $ worth of abrasive and go real slow. You will probably spend more $ on abrasives than having it done professionally.... This may be one of those things where you think you are saving $ but spending more and getting a marginal job.....

[rebel heart]

Originally Posted by Cheechako

yeah... good point. I assume the mill grinding is done with abrasive, but as a note to the OP... dont use anything that has been used previously on steel. Grinding a 2" wide SS bar is going to use many $ worth of abrasive and go real slow. You will probably spend more $ on abrasives than having it done professionally.... This may be one of those things where you think you are saving $ but spending more and getting a marginal job.....

Understood.

Like I said, right now it's just a choice between new mill finished stainless done however I can versus leaving decades old ones installed with (probable) corrosion. When I yank them if they look fine I won't sweat it, but I've seen that crevice corrosion in other stainless so any hints of that and in go the new bars.

I'll source out some silicon bronze so that in the fall before we leave the country I can have "real" ones made up. Right now it's just to not have the stick fall in the water for the next few months.

[roverhi]

I wouldn't think of trying to make stainless chainplates without a drill press. Drilling 3/8" or any hole in stainless is so much easier with a drill press. Practically a walk in the park compared with haing to drill it with a hand drill. You can buy the stainless plate in the correct widths, thickness and cut to length from the material suppliers. That leaves rounding the top edge, drilling the holes and polishing. A lot less painful than having to do all the work yourself.

Good luck on finding silicon bronze flat stock. It just doesn't seem to be available anymore. You can get round bar but not flat. Aluminum Bronze 954 is available and seems to have the right specs but couldn't get anyone to tell me if that material is suitable for chainplates.

[casual]

Real Life,Rudder shoe attached with stainless bolt's,while cleaning aft bilge section hit one of the nuts affixing shoe BIG LEAK bolt crumbled,BIG PUMP,and a dive to push new bolt thru,found all bolts in simuliar shape.Thank Goodness I,wasn't in the Ocean.Wonder why, had all above explained lack of oxygen in the water.

[perchance]

[QUOTE=rebel heart;1010375]I have some 314 barstock that I want to make some chain plates out of, but they're mil finished. If I have the time I'll polish them if that's unnecessary, but if there's some sound metallurgical reason to polish them I'll do it for sure.

Thanks metal guys.[/QUOT

Google "Pasivating stainless steel". It is a chemical process designed to increase the corrosion resistance of stainless steel.If you could find passivated stainless flat bar "off shelf" you may want to go that route.

[Jim Cate]

G'Day RH,

In the SD area I am sure that there are shops that can do electropolishing, a process sort of like reverse electroplating. It is considerably less expensive than mechanical polishing, and leaves an attractive and passive surface that resists crevice corrosion quite well.

You might consider having your SS chainplates done as you fabricate them. Doing it twice seems kinda silly to me, and the advantage of silicon bronze over proper SS is pretty nebulous.

Cheers,

Jim

[osirissail]

Being of Scottish stock I am rather frugal (a.k.a cheap) so I buy mill finish stainless steel plate or bar and finish polish it myself. It is not difficult, just time consuming.

You get a "1/4 sheet size" finishing sander (one of those with a square pad that takes 1/4 sheet of flat sand paper) and then start with either 80 or 120 grit sandpaper until the major ridges, valleys and marks are gone. Then you work down the entire range of sandpapers until about 400 grit. Then switch to automotive finish sanding paper in grits from 600 -> 1000 -> 1200 -> 1500 and finally 2000. By 1500 and then 2000 grit paper you will have a mirror finish on the stainless steel. Starting with the automotive finish paper I use a sponge with water to keep the surface clean and cool.

Passivation is merely chemcially removing the ferrous ions/particles and leaving the chromium behind. This can be done with Nitric Acid which is not generally available so I use Wichard Wichinox. If that is not available there are other "polishes" that have "acid" in them and claim to passivate Stainless.

Inspecting plates I look for surface pitting or cratering that looks like something is "eating" into the metal. This is the telltale that the corrosion has started and the plate is probably a goner. If that is not there then polish up the old plate and inspect it again. If it is shiny and smooth put it back.

I have found the key to successful drilling of holes in stainless is a drill press with very low speed, cutting oil, and "cobalt" drill bits that I get from Home Depot or other tool shop.

[mlibkind]

Originally Posted by osirissail

You get a "1/4 sheet size" finishing sander (one of those with a square pad that takes 1/4 sheet of flat sand paper) and then start with either 80 or 120 grit sandpaper until the major ridges, valleys and marks are gone. Then you work down the entire range of sandpapers until about 400 grit. Then switch to automotive finish sanding paper in grits from 600 -> 1000 -> 1200 -> 1500 and finally 2000. By 1500 and then 2000 grit paper you will have a mirror finish on the stainless steel.

This was just the information I was looking for. I am interested in polishing 2.5-inch diameter round tube. Any suggestions for that since it is not flat?

Also, does it help to do any polishing with some type of compound?

[mitiempo]

Passivated and electropolished gives the best results. Here is a link with more info from a surveyor and a pic of the corrosion of a chainplate where it was buried in a deck.

Sailboat Rig Problems - J. Stormer

[Cheechako]

Originally Posted by mlibkind

This was just the information I was looking for. I am interested in polishing 2.5-inch diameter round tube. Any suggestions for that since it is not flat?

Also, does it help to do any polishing with some type of compound?

Yes , it helps alot. I dont remember if it's rouge or what. My buddy does it all the time to SS bolts he uses on his hot rods, a quick sand and polish with compound and they literally look like they've been chromed.
I'll have to ask him again what compound he uses. I imagine it's Google-able. The eaiest way for a tube is to turn it.... like in a lathe.