Polishing Stainless questions....

[Josh Goldsmith]

My dad asked me to make him a cabinet. Well about an hour or so of me telling him no i finally gave in:p . So i am going to be building him a cabinet but my question is more on the countertop problem. We are going to be making a stainless counter top for it. We can easily weld it but i have a hard time polishing it. What i mean by polishing it is making it look like it wasn't welded. I hope i am making sense. Hopefully someone will have some advice cause i really want to make it as professional as possible. Thanks ahead of time. Josh

[Ted Jay]

My dad asked me to make him a cabinet. Well about an hour or so of me telling him no i finally gave in:p . So i am going to be building him a cabinet but my question is more on the countertop problem. We are going to be making a stainless counter top for it. We can easily weld it but i have a hard time polishing it. What i mean by polishing it is making it look like it wasn't welded. I hope i am making sense. Hopefully someone will have some advice cause i really want to make it as professional as possible. Thanks ahead of time. Josh

I'm assuming you are going to TIG weld the SS? What kind of finish are you looking for, polished or brushed look?

[Cliff Rohrabacher]

You can obtain any number of finish types from mirror to brushed. If you want mirror - or anything close - you'll end up using a power policher with stepped grades of abrasive. For a real mirror you 'll liklely end up with diamond compound in the last stages.

My preference is a Brushed finish. It's less finiky doesn't show those infinite little marks that EVERYTHING makes every single time you set anything on the surface.

You can get a brushed finish with a stroke sander.
You can touch it up after installation with a hand sanding block or a really high end inline air driven sanding pad ( not electrical).

Do not - ( as in: DO NOT) use any steel or iron tooling and do not use any abrasive that was used on steel or iron. That practice will cause "Roughing," which is the abrading of iron particles into the surface of the SST where it'll get under the Chromium Oxide passive layer and cause rust pits that will grow and grow and grow.

Do not use any acid on the SST other than a 20% nitric solution and then only for a short periods and nuturalize immediately with baking soda & water. Muriatic Acid will cause a "Flash Attack" which is the stripping of the Chromium Oxide layer which may not self-heal quickly enough to prevent rust from forming. Strong bleach solutions will do the same thing. A base is as bad as an acid. The only acids that can contact SST safely are those so dilute as found in food, Nitric solutions (used in passivation) and Citric (also used in passivation). Straight Acetic acid (vinigar) can cause a Flash Attack if left in contact too long and not nuturalized.

[Josh Goldsmith]

I believe we are going to be using 18g 2-b stainless which i believe is brushed stainless. My dad is the one who is going to be doing all of the welding since he was a certified welder. I would imagine he would be using a tig welder. Cliff you have giving me alot of info that sounds important but to be 100% honest i don't understand half of what you said. I am going to be showing my dad this thread later tonight but if you can put it into lamens terms:D . I think we have all the tools anyone would need to do a profesional look. My goal is to make it look like we bought the countertop. Thanks for the help i really appreciate it. Josh

[Joe Chritz]

I think Cliff is trying to say sand it very very carefully with new abrasives.

If you continue to use finer grits you will eventually end up with a brushed finish or mirror poish.

The pictre should give you an idea on a small scale. The blade is 440C stainless. It is sanded lengthwise with wet/dry paper to 1000 grit. The last passes using a new square for each pass in one direction one time. The guard is 303 stainless and sanded to 1000 then polished with a high speed buffer and a couple compounds.

You can do the same on a bigger surface with power tools. I think the commercial kitchen factories here (there are two) use flap wheels to match the factory brushed when they weld. These are the people who make the stuff for restaurants and such.

Good luck

Joe

[Joe Chritz]

Picture attached now. It was having a "moment"...

[Bruce Page]

Good old maroon Scotch-Brite will give a great brushed finished to almost any metal. It is great for touch up work too.
You can usually find it at the borg.
If you want nice streight lines just clamp a 2X to the top and use it as a guide.

[Cliff Rohrabacher]

I believe we are going to be using 18g 2-b stainless which i believe is brushed stainless. My dad is the one who is going to be doing all of the welding since he was a certified welder. I would imagine he would be using a tig welder. Cliff you have giving me alot of info that sounds important but to be 100% honest i don't understand half of what you said. I am going to be showing my dad this thread later tonight but if you can put it into lamens terms:D . I think we have all the tools anyone would need to do a profesional look. My goal is to make it look like we bought the countertop. Thanks for the help i really appreciate it. Josh

The abrasives part, I thought, was pretty straightforward.

You might thinkabout getting a nice quality inline air sander if you are going to be installing a large amount. Otherwise the suggestions of using guides and hand held pads to ensure a straight line pattern are likely to work great.

I was cautioning you against using abrasives or other things that may force mild steel into the SST vie abrasion sanding grinding or simply rubbing hard one metal against the other. .

The reason Stainless Steel is rust and corrosion resistant is due entirely to what is called in the industry a "Passive Layer" of Chromium Oxide that forms on the surface of the metal. This layer is self replenishing from chromium within the metal so when it's ground, abraded, or otherwise cut the newly exposed metal has a newly forming passive layer.

Things that can interfere with this passive layer include acids and bases as well as ferric metals such as Iron or Steel. Welders often encounter this issue with steel on SST when fabbing up heavy items and use steel welded to SST as a temporary support while the other piece of SST is being positioned They must grind off all traces of the weldment ot rust will set in and be unstoppable.

Same too with SST and steel when machining or performing other tooling operations. Steel will abrade onto the SST and interfere with the passive layer. This is less a problem when using Hardened High Speed Steel tooling instead of mild steel ( becuse of how it abrades) but it happens just the same.
Many machine shops that work exclusively with SST tend to use mostly carbide tooling.

Passivation is the chemical/mechanical process of encouraging that passive layer to form faster or thicker than it would naturally. It can be done with nitric acid solutions in double distilled deionized water using time and temprature. It can also be done using a product called CitriSurf a citric acid passivation solution.

Unless you do something awful you shouldn't need to do anything like Passivation. I mean awful like:
1.) use the same grinder or sand paper on the SST that you were prior using on steel
or
2.) use some really strong base or acid to clean the SST and fail to nutrualize it.

I had a rather nice SST pot that was covered with a thick hard layer of carbonacious crud from over cooking (burning). I caused the pot to rust in pits that ofer a few years kept getting deeper and bigger. I cleaned the blackened carbon from the pot by soaking it in straight household bleach. I tried to wire brush, and sand to get rid of the rust pits. I even tried a dremel and a little stone. No avail.

At the time I was ignorant of the passivation process. I wrecked the pot. I could have saved it with a sand blaster and clean bead blaster media or a passivation process but at the time I had access to neither.