Stainless Steel Glass Balustrades, Frameless Glass Balustardes, Toughened Glass Balustrades, HandRails
Stainless Steel |
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| ASG are toughened glass manufacturers, glass processors, stainless steel fabricators, and we do up-market installations of frameless Toughened glass Balustrading. To complement our range of 12mm clear Toughened glass Balustrading, we can supply and install handrails and posts manufactured with 316 marine grade Stainless steel fixings in satin or mirror finishes. Product information
Stainless steel enjoys a reputation for long term appearance and integrity. The material is an extremely durable alloy but its surface is readily affected by contaminants combined with moisture which over time will lead to rusting.
The word "stainless" is a misnomer, because like all metals, stainless steel may become stained or discoloured over time, impairing its aesthetic look, and longevity. Incorrect specification and fabrication or subsequent handling in coastal environments may cause stainless steel to stain or discolour, impairing the overall look. This discolouration sometimes referred to as "tea staining" has been identified in coastal applications as surface contamination, and if left untreated will eventually penetrate into the stainless steel material and cause rusting.Tea staining does not affect the structural integrity or the longevity of the material if treated in accordance with suppliers recommendations, and it can be controlled. It occurs most commonly within 5km of the surf or within a few hundred metres of a sheltered bay. The staining becomes progressively worse closer to a chlorine or salt source. Wind exposure capable of transporting dust and debris, as well as industrial pollution levels, and higher temperatures with high humidity, can create environments where staining may also occur 20kms from the sea. These same factors will cause even faster corrosion to alternate metals. Keeping a pristine surface finish requires understanding, additional effort and usually additional costs. It is necessary to determine the correct grade of stainless steel at the time of initial planning for the proposed project, and maintenance recommendations will need to be followed after installation to result in problem free finish. Appropriate grade selection
Product such as 304 grade stainless steel is often used for indoor applications, but where there are high aesthetically critical expectations for outdoor use, a number of more corrosion resistant stainless steel grades can be considered (starting from 316 which is often referred to as "marine grade" then to 2205, and further to super duplex grades and other specialized products). 316 grade is often selected as a minimum specification within 5kms of a surf coast. Stainless steel in 2205 grade resistance to rust is extremely high but this very high end product as well as other super duplex grades are prohibitively expensive with prices starting from over four times the price of the regularly specified grades of commercially produced 316 exterior grade stainless steel products. These products are used for aggressive applications such as with potential splashing by sea water, unwashed areas, or applications where no staining can be tolerated. Limits for different alloys immersed in water at ambient temperature and neutral pH.
Values are conservative. Smooth clean surfaces at high flows can take higher levels (ASSDA publication) Surface finishes Rough surfaces more readily promote tea staining, whereas the smoother the surface the more likely for the surface to stay cleaner. Rougher surfaces will more easily collect and retain chlorides and other contaminants. |
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Pre-cleaning prior to installation
Surface iron contaminants may be cleaned by "pickling" where dilute Nitric acid is used to clean the surface of the stainless steel.Pickling paste is also used to remove the black weld burn marks to remove the burnt colour. This process is of some benefit to the material surface rendering it more passive or resistant to tea staining.Electropolishing This process is a more effective measure for passivating the material. Using an electrolytic tank through which electric currents (positive & negative) are passed, a strong magnetic field is created.The main ingredients of stainless steel are Iron Oxide, Nickel, and Chromium. 316 marine grade stainless steel is manufactured in various countries such as Finland, Sweden, New Zealand, Japan, India, and China. The quality based on the amount of Nickel and chromium content per tonne of 316 grade stainless steel metal has varied downward in proportion to the Iron Oxide content, country by country, as the prices for Nickel and Chromium have escalated over the past years, and the demand for more moderately priced 316 marine grade stainless steel has escalated. The Electropolishing process produces an electrochemical reaction to the surface of the stainless steel metal of a magnitude which removes a microscopic layer of Iron Oxide metal from the surface of the stainless steel. The process is similar to the reverse of chrome plating where a metal is coated with a layer of chrome in an electrolytic tank. The process does not attract a metal coating but the process removes Iron Oxide from the surface of the metal to render it less able to allow impurities to attach to and corrode the Iron Oxide in the stainless steel metal. This results in a brighter surface which is more resistant to tea staining and rust. Electropolishing, being the reverse of Electroplating, the Iron Oxide metal is removed rather than being deposited or coated with another metal. The stainless steel article to be electropolished is made the anode in an electrolyte which, when a low voltage is applied, forms a polarized film over the entire surface. This film is thickest over the microdepressions in the stock material and thinnest over the microprojections. Where the polarized film is the thinnest, electrical resistance is the least and therefore the rate of metallic dissolution is the greatest. Electropolishing effectively removes the microscopic high points much faster than the rate of attack on the valleys or microdepressions. Stock is removed as a metallic salt and can be controlled for removal of Iron Oxide to about 5 microns depth. It is believed that the polarized film is responsible under proper operating conditions, for brightening and slightly smoothing the metal surface. By removing a small amount of metal from the surfaces, Electropolishing also removes any contamination on or just under the surface. This enables a much stronger subsequent weld or braze to be achieved, many times with less heating or brazing material being used. Typical other applications for Electropolishing include hospital, medical, and surgical equipment, bone and joint implants, vacuum equipment, dairy, food, and beverage processing and handling equipment, paper mill equipment, electronic and communication parts, valves and fittings for automotive and truck parts, and all shapes of wire goods. These parts can range in size from a small nut or bolt, to tanks with thousands of litres capacity. Contributors : Jack Mathews Metaglo Pty Ltd / Sydney Australian Stainless Steel Development Association Brisbane Electroplating Engineering Handbook Lawrence J. Durney Van Nostrand Reinhols Company, Publishers, USA |
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