Spotlessstainless Question

[Roger Long]

Mainesail and Rich,

Do you think this stuff:

http://www.spotlessstainless.com/

as Mainesail discussed here:

http://forums.sbo.sailboatowners.com/showthread.php?t=121623&#post740600

will do a sufficient job of passivating my refurbished chainplates after they are mirror polished and thouroughly cleaned or should I go the whole route of having them dipped and processed in the conventional fashion.

(Like this)

http://www.mmsonline.com/articles/how-to-passivate-stainless-steel-parts

 

[RichH]

The msds, verbally given from the proprietor in another forum, indicates a heavy citric acid base, .... plus.

Usually chemical passivation is inferior to mirror polishing + electropolishing but on your triangular shape there will be no way to do the grinding/polishing, etc. on 'all' surfaces .... so, I'd recommend doing it this way but first to grind/polish where possible, then 'etch'. However, 'Spotless stainless' is going to be a 'dilute' mix (for 'consumer usage safety') and therefore will take a LOT of time to do a proper chem. passivation .... Id go the 'industrial strength' route, instead.

 

[Roger Long]

will take a LOT of time to do a proper chem. passivation ....

I've got about four months, will that be enough?

Is there a difference between doing it quickly with a strong solution and slowly with a weak one?

Could I overdo it with the weak solution?

 

[RichH]

Here ya go for a brief methodology for various chemical passivation methods... pre-cleaning being very important. Concentration (dilution) of the fluids only changes the time rate ... you 'should' get the same results.
A general rule of reaction rates is: for every 20°C increase in temp. you will 'double' the reaction time.
http://www.mmsonline.com/articles/how-to-passivate-stainless-steel-parts see figure 4. but prewash with NaOH, rinse, etch, rinse, then post wash with NaOK, rinse ... you can find this 'Carpenter/citric method' in the documentation.

---------------
Caution for 'other' readers of this post - the above URL explains the formulation including the use of severe 'caustics', etc. If you dont have the chemical knowledge/expertise in their use, 'dont mess' with this.

 

[Roger Long]

If you dont have the chemical knowledge/expertise in their use, 'dont mess' with this.

That would include me.

 

[jibes138]

Rich is right on. I run a factory that does this process every day. The environmental compliance requirements and safety personal protective equipment along with required process knowledge will put this beyond the scope of DIY's. Just give it to a shop that does this. They can add it to the basket of parts they are running anyway so the cost to do an extra piece won't be much. Be careful though, they may try to gouge you. This is standard processing in aerospace products versus the polish and electropolishing Rich recommends. I am not implying it is better, only that is is adequate for the purpose and less costly.
Polishing the surface reduces the exposed area and surface defects that act as stress risers. As a part is stressed the atoms are in a high energy state and around the stress risers are even more so. Since they are in a high energy state they are also more susceptible to chemically reacting thus resulting in things like crevis corrosion. So polishing is good but use an inert polishing compound that won't end up microscopically imbedded in the material. Don't use something like a wire brush wheel for instance.

 

[RichH]

Sanding, grinding and polishing is quite easy for small parts ... just time consuming. Use iron-free compounds for polishing - the best is diatomaceous earth mixed in 'white clay' - *Kieselgür" or "tripoli". Use on a high speed fabric wheel and polish to a mirror surface.

 

[Bob S]

Boy I learn a lot from this site. RichH do you mean jewelers rouge or a pumice?

 

[RichH]

Neither.
White metal polishing is best done with a mixture of fossilized marine 'diatoms' and fine clay mined from ancient seabeds. Most industrial hardware stores, etc. will have this in 'stick' form ... just a 1" diameter X 6" long cardboard covered 'stick' and will have for "White Metals" on the casing. The material will be somewhat grey in color, the 'whiter' the better quality. Its sold in various 'grit' sizes. The 'absolute best' is called "TRIPOLI" which is mined near the mediterranean city of Tripoli - becoming rare and quite expensive.

Rouge is for polishing 'red metals' - brass, bronze, copper, gold, etc.