Polishing  Stainless Steel Boat Trim

A. Kip:

Sure it is Stainless? If it is, it must be a very poor grade because Stainless doesn't rust. It might be wise for you to check the material with a magnet. (Stainless is nonmagnetic). If it is Chrome the best you can do is constant upkeep and waxing to prevent further rusting of the surface.

A. I disagree. Stainless will corrode in 23 years of exposure to salt water. Ascertain that it is stainless. If it is non-magnetic in this case you can be pretty sure it is.

If so, get a commercial rust remover to get to clean surface and then use an extremely fine abrasive-a rouge-to get to a mirror finish. This will only work if you still have a smooth surface. That is, if the corrosion hasn't roughened it.

Mike Mcguire
- Pittsburgh, Pennsylvania
 

A. Kipp:

You definitely can get rust on stainless steel parts on a boat that is in a salt water environment for that long. I agree that you can confirm that it is stainless with a magnet. It is highly unlikely that any boat manufacturer would use magnetic grades of stainless for the exterior parts of a boat.

There are many rust removing compounds on the market. You can probably buy one at the hardware store. If you cannot find something, contact us and we will send you some. Be careful that these products are not put on sensitive surfaces or carbon steel parts without testing carefully first.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

 

A. Mike/Lee:

Sorry guys, but nowhere in the question did the gentleman mention saltwater. Are you assuming saltwater? I do realize that Stainless will, to some degree, allow some amounts of rust to form. However, typical boat fittings are highly polished from the factory and unless those fittings were damaged or severely scratched (giving the rust a place to start)it is highly unlikely that the amounts of rust that the gentleman speaks of could occur on the fittings if they were truly an even decent grade of Stainless. Mild steel can be so highly polished that it will resist rusting for a period of time due to the fact that the corrosion needs an edge to begin its' work.

Bill Miller
- Shinnston, West Virginia

A. Sorry friends, but let's see the cause a bit technically. There is no good or bad stainless steel. There are grades in stainless steel like 304, 316, 316 L and so on. These are austenitic microstructure and are non-magnetic for all practical purposes. 400 series Stainless Steel has martensites and is magnetic. Correct grade used for a given service is good. For corrosion resistance say 316 is good but for kitchen knife 410 is good. In this case if it is sea weather then 316 or 316L needs to be used. For sweet water lake boats 304 is good enough. In spite of all this, Stainless after extensive use can show corrosion due many reasons. Not right to discuss why here, as "Corrosion in Stainless Steel" is a subject by itself and can need at least a chapter. The answer I see is:
1)Make sure it is Stainless steel (any grade)
2)If yes, use anti-rust and then use 3M fine grit polishing pads/paper and hand-polish it to a uniform clean shine. 3)If you want luster, use wax and a leather wheel 4)To fine finish use wool/cotton wheel. On wheels use about 1400 RPM. If this is not stainless steel.....I do not know simple answer...but if I was there, I would change it to Stainless Steel as nothing to beat SS for such service and looks.

A. Hey Kipp,
Most likely the stainless is 304 (18/8). If it is just surface rust try 220 to 320 or scotch-brite pads to remove the corrosion then hit it with a (green) abrasive buffing wheel. This should get it to a satisfactory mirror polish. Either take the trim off or be careful not to burn through the gel-coat. Next and as the last step before re installing, have the trim electropolished to greatly increase the corrosion resistance.

If the trim is badly pitted then mechanically sanding the pits out with 120-320 grit abrasive then buff. This can be tricky if the trim has a radius because disk sanding can create flat spots that will show more obviously when mirror polished (there is an art to this.) Again have the parts electropolished.

If you're not super picky about having a top notch aesthetically pleasing "mirror" pit free polish, then just have the parts electropolished. This will remove all rust and inhibit any further corrosion. This can be done faster/cheaper then having a shop mechanically remove/repolish.

Bill and group
Depending on the part, most manufacturing processes on stainless are tooled, formed, drilled, tapped etc with tooling that contaminates and puts voids in the passive layer on the stainless. Unless this contamination is removed and the passive layer regenerated by pickling passivating or electropolishing it is just a matter of time before corrosion starts.
As an example, a lot of times you will see boat railing stanchions glued and fastened to the decks show signs of corrosion on the screw heads used to secure the railing. This is due to the contamination of iron compounds from carbon steel screwdrivers used to fasten the screws.
The same happens when you have stainless steel rub-rails that have been gouged or scratched by carbon/mild steel dock hardware.

As a test you can take two pieces of the same stainless. Drill or take a nail and deeply scratch both pieces. Passivate, Pickle, or electropolish one of the pieces and subject both to accelerated corrosion testing (salt fog chamber, or bucket with salt water and and air pump and bubbling stone.) It will be very apparent that the untreated stainless will have failed.

Hope this helps