Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 12-08-2012, 11:16   #16
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,369
Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

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.....
__________________

__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 12-08-2012, 14:45   #17
Senior Cruiser
 
rebel heart's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Posts: 6,190
Images: 3
Quote:
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.
__________________

__________________
rebel heart is offline   Reply With Quote
Old 12-08-2012, 15:15   #18
Senior Cruiser
 
roverhi's Avatar

Cruisers Forum Supporter

Join Date: Aug 2005
Location: Kona, Hawaii, Carlsbad, CA
Boat: 1969 Pearson 35 #108 & 1976 Sabre 28
Posts: 6,006
Send a message via Yahoo to roverhi
Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

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.
__________________
Peter O.
'Ae'a Pearson 35
roverhi is offline   Reply With Quote
Old 12-08-2012, 15:25   #19
Registered User

Join Date: Jul 2011
Location: Stuart Fl
Boat: Cabo Rico 38
Posts: 692
Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

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.
__________________
casual is offline   Reply With Quote
Old 12-08-2012, 16:19   #20
Registered User

Join Date: Dec 2008
Location: ontario canada
Boat: grampian 26
Posts: 1,743
Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

[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.
__________________
perchance is offline   Reply With Quote
Old 12-08-2012, 16:26   #21
Senior Cruiser
 
Jim Cate's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 11,466
Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

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
__________________
Jim and Ann s/v Insatiable II , lying Port Cygnet, Tasmania once again
Jim Cate is offline   Reply With Quote
Old 12-08-2012, 17:30   #22
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

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.
__________________
osirissail is offline   Reply With Quote
Old 17-02-2014, 20:21   #23
Registered User

Join Date: Nov 2009
Posts: 122
Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

Quote:
Originally Posted by osirissail View Post
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?
__________________
mlibkind is offline   Reply With Quote
Old 18-02-2014, 00:19   #24
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,743
Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

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

Attached Thumbnails
Click image for larger version

Name:	DLchainpl1.jpg
Views:	65
Size:	38.4 KB
ID:	76355  
__________________
mitiempo is offline   Reply With Quote
Old 18-02-2014, 10:03   #25
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,369
Post Re: Does Stainless Steel Finish Matter For Corrosion Protection Or Anything Else ?

Quote:
Originally Posted by mlibkind View Post
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.
__________________

__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Reply

Tags
corrosion

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 23:40.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.