What's up with stainless steel these days?

[Patrick S/V Shangra-La]

I used RustAid from lowes

put it on with a spnge (use gloves it saustic). Let it sit for 1 to 2 minutes and the rust vanished. Wrinsed off well with fresh water. It doesn't seem to have hurt the jelcoat, and is much easier than scrubing.

 

[RichH]

Surface finish quality of stainless is just as important

as various alloy grades (of 300 series).Any 300 series stainless that is fully exposed to air and that is not either 'passivated' nor polished (or electropolished) to a mirror finish will 'rust'. Any small crevice even microscopic crevice will be the initiation site for rust in such stainless. With respect to various grades of stainless, 316 is best suited for 'seawater' ... but still needs that perfect surface finish to prevent rust and stains. For quality stainless to prevent 'rust' you need the material to be certified for surface roughness to be approximately "10 micro-inchs Ra" .... and this is 'near absolute perfection' with respect to polishing. Passivation, electropolishing and mechanical mirror polishing are not cheap and the 'foreign' supplied material will usually be cheap because of 'cutting corners' in the polishing process. You usually get what you pay for; ..... when you buy 'cheap' expect cheap. Stainless that's rusting ..... was specified by an 'accountant'. So, if your stainless is 'rusting' it means that further polishing is needed to 'flatten down' the surface roughness. Can be done first by sanding down with successively finer and finer grades (220-->320-->400-->600--->1000 grit paper, etc) of sandpaper then bright mirror-polished with a high speed (sewn) fabric polishing wheel and appropriate polishing compounds for stainless ('Tripoli', etc.) You dont stop polishing until the piece is 'perfect' ... no crevices, no irregularities, no weldsplatter, no mill marks, no scratches .... perfect, or it 'will' rust. ... after mirror polishing, then for added 'passivity' take the part and get it electropolished.

 

[The Guy from PEI]

Rust, Rust and more Rust........

Just another thought to add......Last year my friend and I welded together a set of back stantions & rails for his boat (26 Macgreggor). When he was cleaning up the welds he was too "cost concious" to use a new wire wheel. The only spots he got rust on was where he "cleaned it up". This was because he had used the tool previously on other metals that rust easily. It is the same with hand tools. You can get rust from metal filings by using your tools on non stainless projects. I keep a seperate set of tools just for work on the boat because of this. I keep all my "mechanics tools" seperate. One of those multi bit / drive sets are great and always on sale at sears or wherever. On using steel wool - If you have ever left it in a little bit of water like the bottom of the bucket, you notice that it rusts quite easitly. All the little strands break away when you use it ( notice that the steel wool isn't as thick or big as when you started) and find nice little crevases to hid in. It will rust and stain you deck / work area. Some of the special polishing compounds for stainless that should be used with fabric / cloth polishers are really the way to go even though they aren't always as abraisive.Good Luck

 

[Ross]

The subject of surface finish is interesting.

I bought the 316L stainless steel for my chain plates from Carpenter Steel. I drilled it, bent it to shape, and installed it 12 years ago with the mill finish still intact. There is no sign of rust and there never has been any. A bright polish looks nice but the alloy is also the critical factor in rust prevention. There has been mention of using steel wool to aid in rust removal but that leaves traces of low alloy steel on the surface. Those traces will also rust. Scotch Bright is a much better choice.

 

[Ralph Johnstone]

Take a Close Look .........................

............ at the most neglected derelict boat in you marina and pay close attention to its stainless stanchions and railings. I doubt you will find a trace of corrosion on them. Note the tubing surfaces with tight radius bends and how they became rough with cold working when they were formed. No corrosion. They haven't seen a coat of wax or anything else for years, but still no corrosion.Chromium makes stainless steel stainless and SS from China is notoriously below specs for chromium in stainless steel.Best regards,s/v Island Hunter

 

[jimq26]

This is a good link re s/s and corrosion.

(nm)