Stainless Steel Tube

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Tube is open at both ends and have hollow cross section, its length and around the larger steel, according to production methods can be divided into seamless and welded steel pipe, steel pipe size specifications with the appearance (such as the diameter or side length) and the wall thick that a wide range in size from very small diameter capillary until a few meters in diameter, large diameter pipe. Steel can be used for pipes, thermal equipment, machinery, petroleum geological exploration, container, chemical industrial and special purpose. 
Classification of Steel: Seamless and welded steel points (pipe joints) two categories. By cross-section shape can be divided into tube and shaped tubes, round steel is widely used, but there are some square, rectangular, semi-circular, hexagon, equilateral triangle, octagon and other special-shaped pipe. For the steel pipe to withstand fluid pressure test should be conducted to test the pressure of hydraulic capacity and quality, the provision does not leak under pressure, wet or expansion of qualified, some steel but also according to the requirements of the standard or demand side, curling test , flaring test, flattening tests.

Steel tube size deviations comparison between international standard

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Comparison between domestic and international size deviations

尺寸（SIZE） 标准(SPECIFICATION) 外径尺寸 SIZE 外径允许偏差  PERMISSIBLE VARIATION 外径尺寸  SIZE 壁厚允许偏差  PERMISSIBLE VARIATION 尺寸  SIZE 允许偏差  PERMISSIBLE VARIATION GB/T14975-2002 [10,30] +0.30/-0.30 S≤3 (+,-)14% [1.0,30.] +15/-0 (30,50] +0.40/-0.40 S>3 (+12%/-10% D>50 (+,-)0.9% GB/T14976-2002 [6,10] +0.20/-0.20 (0.5,1.0) (+,-)0.15 +15/-0 (10,30] +0.30/-0.30 (1.0,3) (30,50] +0.40/-0.40 S>3 (+12%/-10% D>50 (+,-)0.9% GB13296-2007 [6,30] +0.15/-0.20 D≤38 +10/-0 (30,50] +0.30/-0.30 D>38 +20/-0% D>50 (+,-)0.75% +22/-0% ASTM A213 D<25.4 +0.10/-0.10 D≤38.1 +20%/-0 D<50.8 +3/-0 [25.4,38.1] +0.15/-0.15 (38.1,50.8) +0.20/-0.20 [50.8,63.5) +0.25/-0.25 D>38.1 +20%/-0 D≥50.8 +5/-0 [63.5,76.2) +0.30/-0.30 [76.2,101.6] +0.38/-0.38 (101.6,190.5] +0.38/-0.64 (190.5,228.6] +0.38/-1.14 ASTM A269 D<12.7 +0.13/-0.13 (+,-)15% +3.2/-0 [12.7,38.1] (+,-)10% [38.1,88.9) +0.25/-0.25 +4.8/-0 [88.9,139.7) +0.38/-0.38 [139.7,203.2] +0.76/-0.76 ASTM A312 [10.29,48.26] +0.40/-0.80 10. 29～73.03? +20%-12.5% 88.90～762.00 t/D≤5%? +22%-12.5% 88.90～762.00 t/D≤5%?? +15%-12.5% >508.00 t/D焊接管式更大所有比例? +17.5%-12.5% +6/-0 (48.26,114.30] +0.08/-0.80 (114.30,219.08] +1.6/-0.80 (219.08,457.20] +2.40/-0.80 JIS G3459 D<30 +0.30/-0.30 S<2 (+,-)20 D≥30 +1%-1% S≥2 (+,-)10% JIS G3463 D<40 +0.25/-0.25 D<40:S<2 +0.40/-0 D≤50:L≤7 +7/-0 [40,50) D<50:L>7 长度每增加３M或 其零数在上面的正 允许偏差加上３mm， 最大15mm [50,60) [60,80) +0.30/-0.30 D<40:S≥2 +20%/-0 [80,100) +0.40/-0.40 [100,120) +0.40/-0.60 D>50:L≤7 +10/-0 [120,160) +0.40/-0.80 D≥40 +22%/-0 D>50:L>7 与D<50:L≥7m 内容相同 [160,200) +0.40/-0.60 D≥200 +0.40/-1.60 DIN17456 DIN17458 D2 (+,-)1.0%(+,-)0.5min T3 (+,-)10% 0.2min D≤40:L 1m D≤40:L:(1-2]m D≤40:L:(2-3]m D≤40:L:(3-4]m D≤40:L:(4-8]m +1/-0 +2/-0 D3 (+,-)0.75%(+,-)0.3min +3/-0 T4 (+,-)7.5% 0.15min +4/-0 +5/-0 D4 (+,-)5% 0.1min 40<D<168 L≤6m +5/-0 L>6m +10/-0 ASTM A511 TABLE3 D<12.7 +0.13/-0.13 (+,-)15% +3.2/-0 [12.7,38.1) (+,-)10% +4.8/-0 [38.1,88.9) +0.25/-0.25 [88.9,139.7) +0.38/-0.38 [139.7,203.2) +0.76/-0.76 [203.2,219.8) +1.14/-1.14 [219.8,323.85] +1.57/-1.57 ASTM A511 TABLE4 D≤76.2 +0.56/-0.58 S≤2.77 (+,-)16.5% +4.76/-0 2.77<S≤4.37 (+,-)15% 4.37<S≤5.16 (+,-)14% S>5.16 (+,-)12.5% (76.2,139.7] +0.79/-0.79 S≤2.77 (+,-)16.5% 2.77<S≤4.37 (+,-)15% 4.37<S≤5.16 (+,-)14% S>5.16 (+,-)12.5% (139.7,203.2] +1.19/-1.19 4.37<S≤5.16 (+,-)14% S>5.16 (+,-)12.5%

Cold Rolled Steels

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Cold rolled steels provide excellent press formability, surface finish, and thickness and flatness tolerances. Steel companies manufacture three groups of low- or ultra-low-carbon grades to meet a variety of customer formability requirements: CS Type B, DS Type B, EDDS, and EDDS+. They also produce HSLA steels and structural steel grades for those applications that require specified strength levels. 
Cold rolled steels can also be specified as dent resistant or bake hardenable for applications that require dent resistance after forming and painting. Each grade can be processed with several surface finishes depending on customer requirements. Lubricants can be applied to enhance formability and to avoid at-press lubrication.

Cold rolled steels have the following features:

Excellent Surface Appearance. Cold Rolled Steels have manufacturing controls in place assuring consistent surface quality to satisfy customer requirements. 
Formability. Cold Rolled Steels can be used to produce parts containing simple bends to parts with extreme deep drawing requirements. 
Paintability. Due to stringent surface roughness controls, Cold Rolled Steels are readily paintable using essentially any paint system. 
Weldability. Cold Rolled Steels can be joined using virtually any accepted welding practice. 
Standard grades for cold rolled steels are: 
Commercial Steel (CS Type B). May be moderately formed a specimen cut in any direction can be bent flat on itself without cracking. 
Drawing Steel (DS Type B). DS Type B is made by adding aluminum to the mol steel and may be used in drawing applications. 
Extra Deep Drawing Steel (EDDS). Interstitial Free (I-F) steels are made Drawing Steel by adding titanium and/or niobium to the molten steel after vacuum degassing and offer excellent drawability. 
Extra Deep Drawing Steel Plus (EDDS+). Interstitial Free (I-F) steels are made by adding titanium and/or niobium to the molten steel after vacuum degassing and offer excellent drawability. 
Surface Finish
Cold rolled steels are manufactured with a matte finish obtained by rolling with specially roughened rolls on the cold mill and the temper mill. This finish helps to maintain effective lubrication during metal forming and improves the appearance of painted surfaces. Non-standard matte finishes can be provided that optimize the opposing effects of surface roughness on painted part appearance and lubrication during press forming. 


Surface Protection and Lubrication
To prevent rusting in transit and storage, cold rolled steels can be supplied with a rust protective oil film or press forming lubricants. A pre-applied press forming lubricant provides uniform lubrication and eliminates the housekeeping problems. 
A dry film (acrylic/polymer) lubricant can also be supplied by further processing the cold rolled product through a coil coating facility. These specialty organic coatings are easily removed with a mild alkaline cleaner.



Formability and Mechanical Properties
The formability of all steel products is a result of the interaction of many variables, the main ones being the mechanical properties of the steel, the forming system (tooling) used to manufacture parts, and the lubrication used during forming. 
Tight control over chemical composition, hot rolling parameters, amount of cold reduction, annealing time and temperature, and the amount of temper rolling allow the production of high-quality cold rolled steel products to meet customers requirements. Commercial Steel (CS Type B) should be used for moderate forming or bending applications. CS Type B products are produced from aluminum-killed continuously cast slabs and, unless otherwise specified, have a carbon content of less than 0.15%.

To prevent the occurrence of fluting or stretcher strains during forming, CS products are tempered as a normal step in the mill processing.

For more severe forming applications, Drawing Steel Type B (DS Type B) should be used. DS Type B has a controlled carbon content (<0.06%) and is produced in such a manner that parts formed from DS Type B Steel should not exhibit stretcher strain.

Extra Deep Drawing Steel (EDDS) or Extra Deep Drawing Steel plus (EDDS+) should be used for the most demanding forming applications. These steels (also known as Interstitial Free or I-F steels) are produced from a vacuum degassed, titanium stabilized grade. EDDS and EDDS+ have the lowest carbon content available (<0,010%) and have been specially formulated to be most ductile products.

For high strength or structural applications, cold rolled steels are also available in yield strengths up to 50 ksi.


Paintability
Cold rolled steels can be easily painted using a variety of paint systems provided proper care is taken in preparing the material. Prior to painting, the surface should be carefully cleaned with either a solvent or alkaline cleaner. 
Cleaning should be followed by a pre-treatment prior to painting. Zinc or iron phosphates give good results on cold rolled steels. Mild abrasion prior to pre-treating may also be used to enhance mechanical bonding of the paint.

Cold rolled steels can be in general supplied as pre-painted or pre-primed.

Casting Defects in Steels

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Metal casters try to produce perfect castings. Few castings, however, are completely free of defects. Modern foundries have sophisticated inspection equipment can detect small differences in size and a wide variety of external and even internal defects. 
For example, slight shrinkage on the back of a decorative wall plaque is acceptable whereas similar shrinkage on a position cannot be tolerated. No matter what the intended use, however, the goal of modern foundries is zero defects in all castings.

Scrap castings cause much concern. In industry, scrap results in smaller profits for the company and ultimately affects individual wages. Scrap meetings are held daily. Managers of all the major departments attend these meeting. They gather a castings that have been identified as scrap by in inspector. The defect(s) is circled with chalk. An effort is made to analyze the cause of the defect, and the manager whose department was responsible for it is directed to take corrective action to eliminate that specific defect in future castings.

There are so many variables in the production of a metal casting that the cause is often a combination of several factors rather than a single one. All pertinent data related to the production of the casting (sand and core properties, pouring temperature) must be known in order to identify the defect correctly. After the defect is identified you should attempt to eliminate the defect by taking appropriate corrective action.

The system used here for classifying defects is one based on a physical description of the defect under consideration. It is intended to permit an identification to be made either by direct observation of the defective casting or from a precise description of the defect, involving only the criteria of shape, appearance, location and dimensions. This unique system of classification, based upon the morphology of the defects, is more logical than one based upon causes since it requires no prior assumptions to be made.

Seven basic categories of defects have been established, as listed below and for each basic category only one typical defect is being presented here.

1. Metallic Projections
Joint flash or fins. Flat projection of irregular thickness, often with lacy edges, perpendicular to one of the faces of the casting. It occurs along the joint or parting line of the mold, at a core print, or wherever two elements of the mold intersect. 

Possible Causes
Clearance between two elements of the mold or between mold and core 
Poorly fit mold joint. 
Remedies
Care in pattern making, molding and core making 
Control of their dimensions 
Care in core setting and mold assembly 
Sealing of joints where possible. 

2. Cavities
Blowholes, pinholes. Smooth-walled cavities, essentially spherical, often not contacting the external casting surface (blowholes). The largest cavities are most often isolated the smallest (pinholes) appear in groups of varying dimensions. In specific cases, the casting section can be strewn with blowholes of pinholes. The interior walls of blowholes and pinholes can be shiny, more or less oxidized or, in the case of cast iron, can be covered with a thin layer of graphite. The defect can appear in all regions of the casting. 

Possible Causes
Blowholes and pinholes are produced because of gas entrapped in the metal during the course of solidification: 
Excessive gas content in metal bath (charge materials, melting method, atmosphere, etc.) Dissolved gases are released during solidification 
In the case of steel and cast irons: formation of carbon monoxide by the reaction of carbon and oxygen, presents as a gas or in oxide form. Blowholes from carbon monoxide may increase in size by diffusion of hydrogen or, less often, nitrogen 
Excessive moisture in molds or cores 
Core binders which liberate large amounts of gas 
Excessive amounts of additives containing hydrocarbons 
Blacking and washes which tend to liberate too much gas 
Insufficient evacuation of air and gas from the mold cavity -insufficient mold and core permeability 
Entrainment of air due to turbulence in the runner system. 
Remedies
Make adequate provision for evacuation of air and gas from the mold cavity 
Increase permeability of mold and cores 
Avoid improper gating systems 
Assure adequate baking of dry sand molds 
Control moisture levels in green sand molding 
Reduce amounts of binders and additives used or change to other types -use blackings and washes, which provide a reducing atmosphere -keep the spree filled and reduce pouring height 
Increase static pressure by enlarging runner height. 

3. Discontinuities
Hot cracking. A crack often scarcely visible because the casting in general has not separated into fragments. The fracture surfaces may be discolored because of oxidation. The design of the casting is such that the crack would not be expected to result from constraints during cooling. 

Possible Causes
Damage to the casting while hot due to rough handling or excessive temperature at shakeout. 
Remedies
Care in shakeout and in handling the casting while it is still hot 
Sufficient cooling of the casting in the mold 
For metallic molds delay knockout, assure mold alignment, use ejector pins. 

4. Defective Surface
Flow marks. On the surfaces of otherwise sound castings, the defect appears as lines which trace the flow of the streams of liquid metal. 
Possible Causes
Oxide films which lodge at the surface, partially marking the paths of metal flow through the mold. 
Remedies
Increase mold temperature 
Lower the pouring temperature 
Modify gate size and location (for permanent molding by gravity or low pressure) 
Tilt the mold during pouring 
In die casting: vapor blast or sand blast mold surfaces which are perpendicular, or nearly perpendicular, to the mold parting line. 

5. Incomplete Casting
Poured short. The upper portion of the casting is missing. The edges adjacent to the missing section are slightly rounded, all other contours conform to the pattern. The spree, risers and lateral vents are filled only to the same height above the parting line, as is the casting (contrary to what is observed in the case of defect). 

Possible Causes
Insufficient quantity of liquid metal in the ladle 
Premature interruption of pouring due to workman??s error. 
Remedies
Have sufficient metal in the ladle to fill the mold 
Check the gating system 
Instruct pouring crew and supervise pouring practice. 

6. Incorrect Dimensions or Shape
Distorted casting. Inadequate thickness, extending over large areas of the cope or drag surfaces at the time the mold is rammed. 
Possible Causes
Rigidity of the pattern or pattern plate is not sufficient to withstand the ramming pressure applied to the sand. The result is an elastic deformation of the pattern and a corresponding, permanent deformation of the mold cavity. In diagnosing the condition, the compare the surfaces of the pattern with those of the mold itself. 
Remedy
Assure adequate rigidity of patterns and pattern plates, especially when squeeze pressures are being increased. 

7. Inclusions or Structural Anomalies
Metallic Inclusions. Metallic or intermetallic inclusions of various sizes which are distinctly different in structure and color from the base material, and most especially different in properties. These defects most often appear after machining. 


Possible Causes
Combinations formed as intermetallics between the melt and metallic impurities (foreign impurities) 
Charge materials or alloy additions which have not completely dissolved in the melt 
Exposed core wires or rods 
During solidification, insoluble intermetallic compounds form and segregate, concentrating in the residual liquid.
Remedies
Assure that charge materials are clean eliminate foreign metals 
Use small pieces of alloying material and master alloys in making up the charge 
Be sure that the bath is hot enough when making the additions 
Do not make addition too near to the time of pouring 
For nonferrous alloys, protect cast iron crucibles with a suitable wash coating.

Aluminum Temper

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Aluminum TEMPER

   Temper is a measure of a metal's resistance to bending or kinking. It does not refer to how hard the metal is. Low temper, such as H-1 (also referred to as "1/8 Hard"), indicates a tendency to bend or kink permanently when subjected to very little force. High temper,such as H-8 or "Full Hard", indicates a tendency to spring back upon bending.

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TEMPER LETTERS 

 The letters that appear after each alloy number refer to the "temper" of the alloy itself and are independent of the alloy. This means that a single alloy can be available in a variety of tempers and a variety of alloys can be available in the same temper.

   F temper (as fabricated tempers)

   This letter indicates that there has been no effort to control the temper of the material - you receive it "as is".

   O temper (annealed temper)

   Annealing is a process of heating up metal past a critical tempurature whereby the material is relieved of the internal stresses from production or fabrication. It is the lowest temper available (the most easily bent).

   W temper (solution heat treated temper)

   This letter refers to metal that has undergone a specific procedure to produce a temper for a particular batch of metal in order to comply with some specific need of the customer.

  H tempers (strain-hardened tempers)

  This letter designates a process of stretching or compressing in order to impart a particular temper.

     H_1    1/8 hard

     H_2    1/4 hard

     H_3    3/8 hard

     H_4    1/2 hard

     H_5    5/8 hard

     H_6    3/4 hard

     H_7    7/8 hard

     H_8    Full hard

  T tempers (thermally treated tempers)

   These tempers are imparted by heating, quenching, or cooling in a controlled way.

    T1    Cooled after being shaped to its final dimensions during a process involving a lot of heat (such as extrusion), then naturally aged to a stable condition.

    T2    Cooled after being shaped to its final dimensions during a process involving a lot of heat (such as extrusion), then cold worked.

    T3    Solution heat treated, cold worked and naturally aged to a stable condition.

    T4    Solution heat treated and naturally aged to a stable condition 

    T5    Cooled after being shaped to its final dimensions during a process involving a lot of heat (such as extrusion), then artificially aged. T5 is T1 that has been artificially aged.

    T6    Solution heat treated and artificially aged to a stable condition. T6 is T4 that has been artificially aged.

    T7    Solution heat treated and naturally aged past the point of a stable condition. This process provides control of some special characteristics.

    T8    Solution heat treated, cold worked and artificially aged. T8 is T3 that has been artificially aged. 

    T9    Solution heat treated, artificially aged and cold worked A stable temper T9 is T6 that has been cold worked. 

    T10    Cooled after being shaped to its final dimensions during a process involving a lot of heat (such as extrusion), then cold worked and artificially aged. T10 is T2 that has been artificially aged.

Aluminum Alloy Numbers

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Aluminum Alloy Numbers

   These numbers refer to a specific chemical composition of the aluminum alloy - the "recipe" of the metal. Pure aluminum is not a very useful product in any structural work - aluminum products almost without exception are produced from batches of pure aluminum mixed with a number of alloying elements that have been carefully specified by metallurgists in order to maximize particular characteristics of the finished metal. For example, an aluminum alloy that is easily extruded, may be difficult to machine, or an alloy that machines well, may be difficult to weld, etc. This is why there are so may different products in so many different alloys.

The Aluminum Alloys

   Alloy 1100

           A low strength but very workable alloy with excellent corrosion resistance. It is not heat treatable. It is easily welded, however it is soft, and spalls when machined. 

       1100-O: Annealed (or "soft", bendable condition)

       1100-H14: Strain hardened

   Alloy 2011

           A free machining, heat treatable alloy, with fair corrosion resistance, but not very easily welded.

        2011-T3: Heat treated, cold worked and naturally aged

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   Alloy 2024

          Heat treatable with high strength, good machinability and fair corrosion resistance. It welds very poorly.

        2024-O: Annealed (or "soft", bendable condition)

        2024-T3: Heat treated, cold worked and naturally aged

        2024-T351: Heat treated, cold worked and naturally aged

   Alloy 3003

           This alloy is not heat treatable but welds very well and has very good workability. Like alloy 1100 it is somewhat soft and difficult to machine.

        3003-H14: Strain hardened

        3003-H22: Strain hardened, partially annealed

   Alloy 5005

            Poor machinability, good workability and welds very well. It finishes very well, and offers excellent corrosion resistance.

        5005-H34: Strain-hardened and stabilized

       

   Alloy 5052

           Strong, not heat treatable, easily welded, with excellent corrosion characteristics.

        5052-O: Annealed (or "soft", bendable condition)

        5052-H32: Strain-hardened and stabilized

   Alloy 5086

           Very strong, not heat treatable, with excellent corrosion resistance and good weldability.

        5086-H116: Strain-hardened only

        5086-H32: Strain-hardened and stabilized

        5086-H34: Strain-hardened and stabilized

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   Alloy 6061

           Heat treatable, easily welded,  with very good corrosion resistance and finishing characteristics. Very commonly used for architectural products

        6061-O: Annealed (or "soft", bendable condition)

        6061-T4: Heat treated and naturally aged

        6061-T6: Heat treated and artificially aged

        6061-T65: Heat treated and artificially aged

        6061-T6511: Heat treated and artificially aged

   Alloy 6063

           This heat treatable is specifically designed for extrusions, very popular for architectural shapes.

        6063-T52: Cooled from an elevated temperature shaping process and artificially aged

   Alloy 7050

           High strength, excellent corrosion resistence, heat treatable, and weldable, but has poor workability.

        7050-T7451: Heat treated, overaged and strengthened

   Alloy 7075

           Heat treatable, this alloy is the strongest and hardest aluminum alloy. It has good machining characteristics but is not very easliy welded nor is it very workable.

        7075-O: Annealed (or "soft", bendable condition)

        7075-T6: Heat treated and artificially aged

        7075-T651: Heat treated and artificially aged 

General Aluminum Information

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What is an Aluminum Alloy?

   An Aluminum alloy is an alloy primarily of pure aluminum, mixed with different alloying elements that give rise to an entire range of materials, each of which is designed to maximize a particular characteristic such as strength, ductility, formability, machinability, or electrical conductivity.

   

Do the different alloys have a different color or aspect?

   No,  they are aesthetically interchageable. 

 

Is it necessary to specify the alloy?

   Only if there is some physical characteristic of the alloy that will have some bearing on the success of the project (such as corrosion resistence) is it necessary to specify the actual alloy. Generally, the fabricator will purchase the material on the basis of shape or form, and it will arrive with the most commonly available and least expensive alloy present locally. 

   If there is any question of the integrity of the material in any way, the designs must be approved by an engineer, but you will be able to accept substitutions of alloys with confidence that the resulting product will be aesthetically acceptable.

 

What is Temper? 

    This is the quality of metal that describes it’s ability to spring back after it is flexed - in effect, the stiffness. It doesn’t have anything to do with how hard the metal is. Soft temper means that when it is bent, it stays bent, and it doesn’t take much force to do it. Hard temper means that when it is bent, it springs back flat, and it takes a lot of force to put a kink into it. There are several degrees of temper; Soft, 1/4 Hard, 1/2 Hard, 3/4 Hard, and Hard. All metals are subject to temper, and it is a quality of the product that is imparted at the mill. It has no impact on hardness, color, machinability or weldability. However, bending (kinking) and heating to a high temperature can remove the temper and soften the metal at that point. This is called annealing. 

 

What about Finishing? 

    Finishing aluminum is a little more complex than it seems at first.

   Polishing

   It can be polished, with an abrasive finish like #4 satin finish, or even a high polish, but the metal itself is comparatively soft, so these finishes mar easily and they are not recommended without applying a clear organic coating to protect them.

   Lacquering

   Aluminum is an extremely reactive metal. It combines instantly on contact with air to form a thin film of aluminum oxide which in turn is extremely un-reactive and protects the surface from further corrosion. This film is not really visible, but it if the metal is touched, it comes off on your hands as a black smudge. The metal does not stain or visibly corrode (except in extreme chemical  envrionments like salt spray from winter street salt or exposure to seawater) but this smudging is undesirable in most environments. Having said that, there are many architectural environments in which bare aluminum extruded shapes are used with acceptable results.

   The best way for a fabricator keep the silvery look of the parent metal is to abrade the surface with the abrasive finish you require, then lacquer the piece with a clear organic finish. Be sure to use an organic finish that is specifically designed for use with aluminum - conventional finishes will either react with the metal, or will not adhere correctly.

   Anodizing

   This was invented for aluminum (it also works with titanium). It is a process of dipping the aluminum into a liquid solution that contains chemicals that clear the metal surface of its coating of aluminum oxide whereupon a dye is introduced into the solution which can now penetrate the surface of the metal to some depth. The process requires a high current to pass through the metal during the process in order to fix the dye and seal the aluminum with a hard surface, so it must be done in anodizing shops and cannot be touched up on site. It produces an extremely durable tint to the metal, the color of which can be specified (and there are scores available). However, be aware that most of the anodizing colors available are meant to be used in interiors and will fade in the sunlight. There is a broad range of exterior colors available, but you must specify them as such.

   Clear Anodizing

   This is the finish that is most common on natural-colored pre-finished aluminum sheet, available from many architectural metal suppliers. It is simply a non-dyed version of the anodizing process described above, and one of the most common methods to render large aluminum surfaces wear-resistant and corrosion resistant.

   Bronze Anodizing

   This is the extremely common method for producing the extremely durable dark “bronze” finish on architectural aluminum extrusions used in window frames.  The process is identical to those above, and the color is light fast for exterior purposes. The shade of bronze can be specified from extremely light to almost black.

   Hard Anodizing

   The same process, but not for color - it is a method for creating an extremely hard surface to any aluminum material. This is used for example for bolts, sheets that need abrasion resistance etc., or to minimize galvanic reaction between aluminum surfaces and other metals. It is not really architecturally interesting, and somewhat expensive, but has many uses in Industry. It is used in very expensive cookware to impart a hard non-stick surface to pots and pans.