Pickling
Processes, Properties, Advantages
Chemical and anodic pickling processes for removal of scale, discoloration, and other contaminants. The part is pickled for removal of scale and other contaminants. The ElpoChem pickling processes can be used on the following metals, among other materials:
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Stainless steel
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Carbon steel
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Copper and copper alloys
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Aluminum
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Titanium and titanium alloys
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etc.
Pickling sustainably improves the corrosion resistance. Proper pickling results in bare metal surfaces and weld seams that are free of scale and discoloration.
Stainless steel welded plate,
Left side pickled with ElpoNox
Chemical composition of scale and weld seams
(schematic representation)
1. Fe2O3 layer, relatively insoluble in acids
2. Fe3O4 layer, more soluble in acids
3. FeO layer, very soluble in acids
4. Metal substrate
Chemical Pickling
Pickling is done by application of the pickling substances or by immersion of the part in a bath. The dwell time ranges from a few minutes to a few hours.
Anodic Pickling
With anodic pickling, material is removed through the application of direct current in specially equipped plants.
Pickling of titanium and titanium alloys
The effectiveness of pickling and deburring through ChemoLux titanium pickling is especially high for the following materials: titanium and titanium alloys (e.g., TiAl6V4 and Nitinol) as well as niobium, tantalum, and zirconium.
The exposure time depends on the material, the temperature, the metal removal rate, and the concentration of the pickle solution. The pickling time is as a rule between 10 seconds and 5 min.
The ChemoLux titanium pickling processes are used in the following areas:
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Pickling, activation, and deburring with defined removal rate
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Prior to electropolishing as a pretreatment step
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Activation/pickling/deburring of the surface prior to coating or anodization
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Elimination of crack nuclei
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Removal of shine, flakes, and particles
ElpoChem supplies pickle chemicals in the following forms:
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Pickle pastes: For economically efficient treatment of weld seams to prevent scale and discoloration
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Spray pickling: For treatment of components with large surface areas
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Bath pickling: For immersion, sprinkling, forced circulation, and use in spray-pickling chambers
Pickling Application Examples
We would be happy to advise you on your specific surface application:
Telephone +41 44 980 30 30
Passivate
Processes, Properties, Advantages
Passivate: Chemical generation of protective coating
Materials:
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Stainless steel
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Carbon steel
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Copper alloys
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Titanium alloys
In surface engineering, passivation is the spontaneous formation or deliberate generation of a protective layer on a metal to prevent or greatly slow down the corrosion of the base material.
For a number of different metals, it is better to induce passivation layer formation in a defined technical process than to leave it to chance.
Stainless steel
For parts that are loaded immediately after pickling or electropolishing, passivation of the stainless steel is recommended. Through passivation of the stainless steel, the natural process of passivation layer formation is chemically accelerated and the corrosion resistance of the material is noticeably improved.
Copper alloys
Copper and copper alloys have a strong tendency to become discolored when in contact with air and moisture. If necessary, the surfaces can be treated with a discoloration protection treatment containing special inhibitors to protect against corrosion (discoloration).
Passivation Application Examples
We would be happy to advise you on your specific surface application:
Telephone +41 44 980 30 30
Anodizing
Processes, Properties, Advantages
Anodizing
Thickening of existing oxide layer and generation of interference and gray colors via an applied voltage.
Procedure
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Gray anodization – Type II (alkaline with subsequent blasting)
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Gray anodization (acidic without subsequent blasting)
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Color anodizing – Type II
Materials:
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Titanium and titanium alloys
Titanium anodizing
Titanium is a light metal with extremely favorable mechanical material properties and high corrosion resistance. Despite its high price, it is used in the aerospace industry, tank and apparatus construction and in medical technology. Classic processes such as pickling, chemical deburring, and electropolishing are available for chemical surface treatment. In addition the surface can also be anodized, similar to aluminum. There are two variants to choose from for this:
Color anodizing
With color anodizing (Type III anodizing), the naturally existing oxide layer of 4 to 6 nm is strengthened up to 300 nm, generating through this the so-called interference colors depending on the layer thickness.
The thickness of the oxide layer and thus also the interference color can be adjusted exactly using the applied electrical voltage. These layers are used for decorative purposes (jewelry industry) and for identification purposes (medicinal technology).
Exclusively acid electrolyte is used for the color anodizing. The applied voltages are in the range of 10 V to 120 V.
ElpoLux ANOF-A Titanium Anodizing Typ II
ElpoLux Anox-C Titanium Anodizing Typ III
Titanium hip stem:
Electropolished (top)
Color-anodized (below
Gray anodizing
With gray anodizing (Type II anodizing) even higher layer thicknesses are generated in the range up to 1–2 µm. These layers are mainly generated in alkaline electrolytes and used for improving the corrosion and wear resistance. The applied voltages are in the range of 60 V to 150 V.
Gray anodization can also be performed in acidic process solutions to generate layers with thicknesses in the range of 1–2 µm. The applied voltages are in the range of 80 V to 150 V.
In the alkaline process, the part has to be blasted after gray anodization. This step is omitted in the acidic process.
Gray-anodized titanium
Bone plate
Titanium hip stem:
Bone plate
Titanium Surface Finishing
ElpoChem offers extensive consulting and analysis services as well as all process chemicals for chemical and electrochemical surface treatment of titanium.