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Bob uk
Unregistered guest
Posted From: 94.197.122.72
Posted on Monday, 18 August, 2014 - 02:04 am:   Edit PostDelete PostView Post/Check IP

Chrome is electro plated. First the metal is polished and then plated and then polished again. On steel bumpers either nickel or copper is used as an undercoat. The undercoat is also polished. Chrome is porous and will rust.

RR chrome is good but show chrome is better.
To remove small amount of rust polish with aluminum oxide.

But aluminum oxide that fine is unavailable.
Aluminum is made from bauxite. Once made aluminum is immortal and can only exist in two states at normal temperatures. Aluminum and aluminum oxide.

When aluminum is made it immediately reacts with air and aluminum oxide forms of the surface.

Cooking foil has a microscopic layer of very fine aluminum oxide.

Fold foil into wad then using Water rub the chrome and a blue grey residue paste will form. This is a very very fine aluminum oxide polishing paste.

Also it works on paint, stainless and wood lacquer.

Stainless. For SS use baby oil instead of water. And after use baby oil on its own to protect.

Or ky jelly for thicker paste.

(Message approved by david_gore)
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David Gore
Moderator
Username: david_gore

Post Number: 1441
Registered: 4-2003
Posted on Monday, 18 August, 2014 - 08:03 am:   Edit PostDelete PostView Post/Check IP

Bob,

I regret I have to strongly and respectfully disagree with you on care of stainless steel surfaces [stainless steel was one of my specialties during my career as a metallurgist]. Baby oil and/or any other oil is NOT suitable as a protective coating as it will act a "glue" attracting potentially corrosive contaminants and holding them onto the surface of the stainless steel where they may set up a small galvanic cell driven by differential aeration resulting in pitting or general corrosion of the surface. Whoever first used stainless instead of corrosion-resisting did the world a great disfavour as stainless steel is not "stainless" and will corrode in the right environment.

"Stainless" steel's corrosion resisting properties come from a micro-thin layer of Chromium Oxide formed on the surface of the metal by exposure to air/Oxygen. It must remain directly exposed to air/Oxygen for this film to be maintained; exclude the air, add water and access to certain contaminants and the metal will readily corrode.

Cleaning a stainless steel surface especially one that has been mirror-polished is best done with fine powdered whiting made into a paste with clean potable water with a drop or two of neutral detergent added as a wetting agent and gently rubbing the surface to remove any surface deposits and/or stains, let the paste dry and dust off with a clean soft cloth. If the contaminants have corroded the surface, there will be a matt "frosting" appearance or a surface pit depending on the contaminant [contaminants containing Chlorides are especially prone to causing pitting]. Depending on the severity of the corrosion, it may be possible to polish out the degraded appearance from corrosion but this requires an experienced metal polisher and special techniques to avoid overheating the surface and generating a high/low spot which is usually impossible to rectify unless the metal can be "stretcher leveled" to pull out the distortion. Surface deposits should be washed off as soon as possible and not left on the surface for any period of time to minimise surface corrosion.

There is a lot more information I could add however this is best left to specific problems requiring attention. The best advice I can give is to keep stainless steel surfaces clean by removing any surface deposits as soon as possible and avoiding situations where the surface is deprived of contact with air/Oxygen. The use of oils/grease or polishes leaving a "protective layer" on the metal surface should be avoided wherever possible.
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Jan Forrest
Grand Master
Username: got_one

Post Number: 626
Registered: 1-2008
Posted on Monday, 18 August, 2014 - 08:54 pm:   Edit PostDelete PostView Post/Check IP

I've seen videos of slightly rusty chromed parts being brought back to clean in a similar fashion as Bob describes. The difference is that the surface is lubricated with cola before polishing it with cooking foil.
My best guess is that it's the citric acid (to give the drink a 'bite') that's the active ingredient. As I keep a supply of CA crystals on hand for the home brewing of 'country wines' I'll try a weakish solution on the Shadow's front bumper when I get her home again.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 985
Registered: 6-2009
Posted on Tuesday, 19 August, 2014 - 01:17 am:   Edit PostDelete PostView Post/Check IP

Jan,

Your theory makes perfect sense.

Jewelers use what is called pickle to clean pieces between soldering operations and in other instances. One of the favored "natural" pickle compounds is citric acid.

If you look at the article at the link above, cola, lemon juice, and vinegar are all discussed as very weak versions of pickle. The article also notes that it's likely that the term pickle came into being because one of the earliest substances used were alum salts.

Brian
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Bob uk
Unregistered guest
Posted From: 94.197.122.90
Posted on Monday, 18 August, 2014 - 08:47 am:   Edit PostDelete PostView Post/Check IP

Don't use baby oil because of the above which I didn't know but I do now. Thanks Dave.

Baby oil is used on SS marine hydraulic stuff. I shortened a ram for a ship and the designer said use baby oil to protect it while in transit to Brazil.

He said it works well.
But the ram is in a box and not driving through the air at 60 mph.

I put a small amount on a cloth and polish.

Obviously try any idea first on something else. Like the kitchen sink. And push bike chrome handle bars.

My shell is very good. I used the Cooking foil on the sill trims and it made them shinier.

Polishing stainless is differcult and the heat can melt the solder and buckle the SS.

I discovered the foil process tying to make SS bumpers which failed.

(Message approved by david_gore)
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David Gore
Moderator
Username: david_gore

Post Number: 1444
Registered: 4-2003
Posted on Tuesday, 19 August, 2014 - 08:42 am:   Edit PostDelete PostView Post/Check IP

Bob,

Best corrosion protection for a stainless steel component during shipping is to remove the humidity from the air inside the shipping package. Remove the moisture and a corrosion cell cannot form if the surrounding environment is potentially hazardous. As I said previously, exposure to air at all times is essential for the formation and maintenance of the protective Chromium Oxide film on "stainless" steel.

Jan,

Last time I saw the cola formulations, one of the main ingredients was Phosphoric Acid which is more aggressive than Citric Acid. Aluminium is less affected by acids than it is with alkaline solutions; the method you describe to remove surface rust is based on the Aluminium foil, Phosphoric acid and Chromium setting up a galvanic cell to clean the surface and convert the adherent rust to Iron Phosphate which seals the surface to slow down [but not stop entirely] the rusting process. To the best of my knowledge, the Shadow 1 bumper bars were Chromium plated with the "Tri-plate" process, involving a steel pressing given a base coat of Copper, an intermediate coat of Nickel and a finish coat of bright Chromium. Each coat was polished to remove any imperfections before the next stage. Electroplaters using the Tri-Plate process are few and far between these days because of EPA regulations applying to disposal of the used plating solutions and the prices from those who still use this process reflect the high costs involved.

Brian,

Lemon juice contains Citric Acid, Vinegar contains Acetic Acid. These are relatively weak acids unlike the mineral acids such as Hydrochloric, Sulphuric and Nitric Acids. If you encounter Hydrofluoric Acid, discretion is the better part of valour and handling this acid is best left to experienced professionals as it is extremely corrosive especially if it comes into contact with human flesh....................

Selection of a suitable "pickle" solution for metal components is based on the metal/alloy involved, what has to be removed from the surface and the extent of visible corrosion effects that can be tolerated before future processing. A classic case of "not getting something for nothing".
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Bob uk
Unregistered guest
Posted From: 94.197.122.83
Posted on Tuesday, 19 August, 2014 - 09:53 am:   Edit PostDelete PostView Post/Check IP

My aim is to explain how the trade do things at minimal cost. Not lash ups but sensible well engineered "bodges"
Your input is very appreciated because I don't want to wrong foot any body.

I have wiped the trims with white spirit and foil then soapy water then autosolvo and then car wax. It took 20 mins which made me miss Judge Judy. So my whole day was ruined at a cost 10p worth of metal polish. That will teach me not to assume.

The Stianless bumpers were for my SY and S steel is so not malleable it just does not want to be another shape. It has a memory like an elephant.
Mild steel and aluminum have a good memory that is easy to reshape. I bash the memory in as I think about making the metal behave by torture until it does or go to far and the metal will die.

(Message approved by david_gore)
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David Gore
Moderator
Username: david_gore

Post Number: 1446
Registered: 4-2003
Posted on Tuesday, 19 August, 2014 - 12:33 pm:   Edit PostDelete PostView Post/Check IP

"Don't force it; use a bigger hammer!!!!"

Works every time.......

Certain grades of austenitic stainless steel are made to work harden [aka spring back] when they are cold worked; the general rule is the higher the Nickel content and the lower the Carbon content, the less work hardening.

Type 301 is used for manufacturing stainless steel railway carriages for this reason, the material work hardens during roll forming and brake pressing giving a high strength component that retains good impact resistance which is critical if the carriage is ever involved in an accident. Your chances of survival are higher in a properly designed and constructed stainless steel carriage than other alternatives - see the Southern Aurora Violet Town high speed head on crash [Southern Aurora estimated 115/120Km/hr, goods train 40Km/hr]:

http://en.wikipedia.org/wiki/Violet_Town_rail_accident

http://www.t3licensing.com/license/clip/48050073_6100.do

http://www.cfaconnect.net.au/pics-271.html

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