Steel acid treatment

Metal Treatment. After rolling, the oxide scale on sheet steel is removed by acid treatment (pickling) (see Metal surface treatments). Phosphoric acid, a good pickling agent, leaves the steel coated with a thin film of iron phosphates. This process improves mst resistance but presents a problem if the steel is to be electroplated. 

Aikaiinity Bicarbonate (HCOs" ), carbonate (COs , and hydroxyl (OH ), expressed as CaCOs Foaming and carryover of solids with steam embrittlement of boiler steel bicarbonate and carbonate produce CO2 in steam, a source of corrosion Lime and lime-soda softening, acid treatment, hydrogen zeolite softening, demineralization, dealkalization by anion exchange, distillation, degasifying... 

Aikaliniry Bicarbonates (HCOd Carbonates (CO,) Hydroxyl (OH) as CaCO, Steam systems foaming and solid carry over Steel embrittlement (HCO,) and (CO,) Corrosion Distillation Demineralization I..ime and lime soda Dealkalization I lon exchange) Acid treatment liydrogcn zeolire... 

Several processes are used when enameling on steel. The parts to be coated are first alkaline cleaned and rinsed to remove soils. An acid treatment step and rinse follow in that sulfuric acid,... 

Figure 5. Epoxy/steel joint lap shear strength as a function of 57°C water immersion time for the following steel pretreatments (—0—1 citric acid treatment (— —) citric acid treatment followed by...

Conventional conductivity detector cells where the electrolyte is in contact with the electrodes are likely to use electrodes made from 316 stainless steel. A new cell should be treated with 1 N nitric add for about 60 min to deactivate or passivate the cell and stabilize the signal. In fact, such nitric acid treatment is a good idea for all parts of a stainless steel IC system. 

The zinc-air treatment is somewhat simpler because the absence of manganese dioxide means that the acid treatment is not necessary. After the batteries have been opened, they are immersed in sodium hydroxide within a trummel. The fines, containing zinc powder, zinc oxide, carbon and lime are suspended in solution and undergo the same zinc treatment as described above. After washing, the large fraction consisting of polypropylene pieces, steel and carbon are sorted and recycled within specialist industries. 

Historical Perspectives A British patent [2, 3] of 1869 to improve the corrosion resistance of steel hy treatment in boiling phosphoric acid was proposed by W. A. Ross [3]. A number of similar patents appeared in the following years. 

The oxide film on metallic implants is usually very thin (5-10 nm). It is formed as a result of a spontaneous reaction between the metal and the environment. In spite of the common use of immersion treatments in nitric acid solutions, usually known as passivation treatments, they are not necessary to form an oxide. They are often responsible for an increase in corrosion resistance due to removal of surface contaminations or inclusions, as in the case of stainless steels. As indicated in section 9.4.1, there have been reports suggesting that this acid treatment may decrease the corrosion resistance of titanium. 

Any debris from fabrication is removed by a process called passivation treatment in which the surface is treated with, typically, a strong acid like nitric acid. The acid treatment results in an oxide film on the surface which is considered to be more stable than the natural air-formed film. Whether this passivated oxidative film should not be disturbed during subsequent handling is stiU debatable. Stainless steel is sterilized by heat or steam with heat. It was reported that steam sterilization also increases its resistance to corrosion (Sutow, 1990). 

Acidizing treatments are used to stimulate production by the acidic dissolution of undesirable materials on the walls of the producing formation or by pumping acid into the formation to improve permeability. Hydrochloric acid (HCl) is used for limestone formations. Hydrofluoric acid (HF) is added to the HCl for silicate formations. Inhibitors are added to the acid to protect steel tubing during the short period of exposure to acid during injection, and the following period when partially spent acid is returned to the surface. Suppliers use a variety of nonstandardized tests for acid inhibitor evaluation. 

While it is possible to bond to a freshly abraded or cleaned metal surface, chemical treatments are preferred for rendering the metal surface inactive to corrosion over time. For low carbon steel, phosphatising is the recommended pre-bond surface preparation treatment. Stainless steel should be passivated or acid etched, while titanium is usually treated with a hydrofluoric acid pickle. Almninium or magnesium are best treated with a chromate conversion coating. Zinc and cadmium are generally prepared mechanically but a phosphate or chromic acid treatment may be used. Brass and copper may be treated with an ammonium persulphate etch or an acid-ferric chloride etch. 

The following example illustrates how the corrosion efficiency of an inhibitor can be evaluated with LPR. Forty years ago, Hugel tested a variety of inhibitors for steel in 6 M HCl at 60°C and found that alkenyl and aromatic aldehydes were very effective [11]. Cinnamaldehyde was one of the best, providing almost 99 percent protection. Numerous patents have been issued since then on the use of aldehydes, and trans-cinnamaldehyde (TCA) in particular, as steel corrosion inhibitors in acid media have been used to reduce the corrosion of steel during pickling or oil field acidizing treatments. 

Alkalinity Bicarbonate (HCOji, carbonate expressed as CaCOj Foaming and carry over of solids with steam. Embrittlement of boiler steel. Bicarbonate and carbonate produce CO, in steam, a source of corrosion in condensate lines. Lime and lime soda softening. Acid treatment. Hydrogen zeolite softening. Demineralization. Dealkalization by anion exchange. 

Corrosion has been the major factor causing joint failure in the aerospace industry and this is still an issue facing potential industrial and automotive users, particularly if metals such as steel or copper are used [20]. Researchers based in Japan [21] showed that acid treatment of steel does not improve the fracture toughness of bonds with toughened epoxies, but it does increase the fatigue growth... 

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