Saturday, 24 August 2013

Stainless steel renovation and polishing

In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is a steel alloy with a minimum of 10.5% chromium content by mass.

Stainless steel also contains varying amounts of Carbon, Silicon and Manganese. Other elements such as Nickel and Molybdenum may be added to impart other useful properties such as enhanced formability and increased corrosion resistance. [1]

Stainless steel (more correctly stain resistant) is carbon based; it resists staining and does not rust in the true sense of the word. Rust or surface corrosion is when the surface finish becomes scaly or forms loose flakes and where the metal is actually disintegrating.

It is composed of a passive film of chromium oxide and nickel, forming a passive film of chromium oxide. This passive layer is subject to a chemical process; technically called oxidation, which is an electro mechanical process. Normally, stainless steel does not corrode uniformly as do ordinary carbon and alloy steels.

However, with some chemicals, notably acids, the passive layer may be attacked uniformly depending on concentration and temperature and the metal loss is distributed over the entire surface of the steel. 

Hydrochloric acid and sulphuric acid at some concentrations are particular aggressive towards stainless steel.
The passive layer on stainless steel can be attacked by certain chemicals; chloride ion Cl- is the most common of these and is found in everyday materials such as road salt and bleach

Oxidation is an electrochemical process (sometimes called white metal corrosion) it can produce ‘rust spots’ if there are any ferrous metal (brake dust) particulates on the oxidized surface and they are exposed to moisture, but since this is simply a cosmetic condition, it is easily correctable.

There are over 150 different grades of stainless steel. The most commonly used is 304 grade stainless (more correctly stain resistant) steel, which usually contains sufficient chromium (a minimum of 13% by weight) to form a passive film of chromium oxide, which prevents further surface corrosion and blocks corrosion from spreading into the metal's internal structure but will not rust through for maybe a decade, although it may have surface rust. But since this is simply a cosmetic condition, it is correctable.  Stainless steel is welded by using a MIG welding process; the filler rods used in the welding process must be the same grade to maintain stainless steels integrity  

Stainless steel is welded by using a MIG welding process; the filler rods used in the welding process must be the same grade to maintain stainless steels integrity

The most commonly used are the 300 series stainless-304, also known as 18/8 for its composition of 18% chromium and 8% nickel and 316 commonly known as 18/10 stainless, a passive film of 18%chromium oxide and 10% nickel, forming a passive film of chromium oxide, which resists further surface oxidation, this usually lasts for years.

Stainless Steel Exhaust

Using steel wool will leave small particles of carbon steel fibres that become embedded in the surface, which will produce rust spots when they come into contact with moisture. Stainless steel is a ‘soft’ metal that is easily scratched, and  even #0000 synthetic steel wool (which doesn't contain carbon) will cause micro scratches

I suggest that you use 3M Scotch-Brite™ Ultra Delicate Extra Thick Surface Cleaning Pad with a metal polish (P21S Finish Restorer) to provide lubrication, to remove any surface rust.

For really tough stains apply Optimum Metal Polish with a White Scotch-Brite™ pad. It is very important to clean as you go

Innosoft B570 is a specialist deep cleaner developed for stainless steel, that has proven to be equally effective at removing oxidation and contamination on a wide variety of surfaces including aluminium, copper alloys, mild steel and chrome. Containing organic acids and a powerful detergent, it dissolves rust and dirt deposits on contact by penetrating deep into the surface of the metal.

Totally organic, it’s safe and environmentally-friendly way of removing rust and contamination from most metals. By eliminating the need of harsh chemicals that are traditionally used in rust removal, it helps protect both yourself and the planet.

You should also wipe down the exhaust tips and muffler cans and protect them with a polymer sealant or a coating product to maintain its appearance.

Discoloration is common to all stainless steel exhaust components, it’s caused by heat, which typically goes from a gold hue and then darken to a blue /brown. Blue-Job Chrome and Metal Polish has a unique non abrasive, highly concentrated, powder formula, guaranteed to remove bluing and add a long lasting shine, without scratching or dulling the finish surface. Blue-Job will leave your product brilliant, clean, dry and more resistant to future bluing or tarnishing.

1.      Clean surface with P21S Total Auto Wash
2.      Remove any road tar (bitumen) using Optimum Power Clean ™
3.      Use P21S® Polishing Soap – formulated with polishing clay and soap flakes, a mild wheel cleaner that's pH balanced making it simple, gentle, and effective. Its primary function is to return metal to its stock finish. It will remove a lot of the tarnish from their finish, along with any other contaminants
4.      Finish with P21S Finish Restorer

For really tough stains apply Optimum Metal Polish with a White Scotch-Brite™ pad. It is very important to clean as you go.

Metal Polishes

Custom blended polish to suit every metal polishing application. Metal polish for aluminium, silver, brass, chrome, stainless steel, copper or bronze - English Custom Polishing (ECP)

I suggest that you use White Scotch-Brite™ pad with some metal polish to provide lubrication, to remove any surface carbon or rust. You should also wipe down the exhaust tips and muffler cans and protect them with a polymer sealant to maintain their appearance

·         Aluminium Oxide - for chrome and stainless and is used to remove bluing from exhaust pipes, as well as general polishing.
·         Stainless Steel (coarse) - 400 grit finish to a reasonable mirror finish, for weathered or oxidized aluminium
·         Stainless Steel (fine) - an excellent second cut for producing a finer finish on stainless steel
·         Showman’s Blend stainless and aluminium finish polish

Use with Eastwood Company Cotton Buffers

Evapo- Rust  is Non-Hazardous, Non-Flammable, Biodegradable and is non-corrosive to steel and does not harm brass, copper, aluminium, gold, lead, titanium, steel, cast iron, chrome, solder points, vinyl, plastic, rubber, silicone, glass, cork, or wood.. On average, one gallon de-rusts up to 300 pounds of light to moderately rusted steel. Fully immerse the rusted item and check progress in about 30 minutes; no scrubbing necessary. Soak times will vary from 30 minutes to 24 hours depending on severity of rust, type of steel, and temperature.

P21S Finish Restorer – for any metal with or without a clear coat that is faded, oxidized, water marked, burnt, and dirty or has a build-up of brake dust.  This metal polishes deep cleansing formula helps release some of the most difficult build ups. Even on surfaces that look brand new you'll be amazed at how this polish works beneath the surface and removes hard to see contamination. Clean the surface using P21S Polishing Soap and then proceed with the Finish Restorer. For really tough stains apply Optimum Metal Polish with a White Scotch-Brite™ pad. It is very important to clean as you go.

Residual polish should be removed from around rivet or screw heads and from seams as the polishing project progresses. If it dries on it is very difficult to remove. One way to do this is to use a solvent to wipe the surface. The best solvent I have found is isopropyl alcohol (IPA) or mineral spirits as they evaporates slowly and generates fewer toxic fumes. Best method is to use a micro fibre towel to wipe the solvent off and dry the surface

Using cornstarch rather than solvents for cleaning is very effective and eliminates the need to deal with a solvent. Use the micro fibre towel (a terry-cloth towel will provide more abrasion if required) with cornstarch rather than solvents.  It works very well on fresh polish, however if it has dried it generally requires a solvent to remove it. TOTL

First ascertain the type of metal; aluminium, stainless steel, chromium plated or brass? Always use a metal polish specifically formulated for the metal you are trying to polish. OEM’s offer more than one metal type so read the label carefully and when in doubt check with the manufacturer

Alkaline reacts with metals like un-coated aluminium, tin and zinc; this may result to liberation of combustible hydrogen gas and damage to the aluminium.  As always use caution and check the proposed products MSDS

Lower grade Stainless- Use Barkeeper's Friend as it contains Oxalic Acid, which re-pacifies stainless steel.

I hope these TOGWT Detailing Wiki articles will become an asset to anyone who is new to detailing and to the professionals; enthusiast detailer’s and industry experts who seek to advance their knowledge of detailing entry level enthusiast, but to professionals and industry experts as well.

Once you realize how much you don’t know; only then will you be willing to research and enhance your knowledge and understanding

TOGWT Detailing Wiki articles -

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