Rust staining

Stainless steels attacked by sulfate reducers show well-defined pits containing relatively little deposit and corrosion product. On freshly corroded surfaces, however, black metal sulfides are present within pits. Rust stains may surround pits or form streaks running in the direction of gravity or flow from attack sites. Carbon steel pits are usually capped with voluminous, brown friable rust mounds, sometimes containing black iron sulfide plugs fFig. 6.10). 

Rost-feuer, n. grate fire, -flache, /. grate surface. -fleck, m. rust spot, iron spot, -flecken-wasser, n. rust stain remover, rostfleckig, a. rust-spotted, rust-stained. Rostfrass, m. corrosion (of metals), rostfrei, a..rust-free stainless. 

Penetration of rust through an otherwise intact paint film is usually a result of inadequate surface preparation before painting, especially over weathered and hand-cleaned steel. However, superficial rust staining may be traceable to dissolved iron salts, e.g. in bilge water from a ship s deck. 

Survey coatings for surface cracking, delamination, rust staining, or bulging. 

This formulation is designed to be used "as is" and is particularly effective in the removal of scale build-up and rust stains. 

Oxalic acid is a poisonous compound but an excellent reducing agent that is used to remove rust stains and to reduce chemicals in the laboratory. Suppose that 25.00 mL of a solution of oxalic acid, H2C204 (4), is titrated with 0.100 M NaOH(aq) and that the stoichiometric point is reached when 38.0 mL of the solution of base is added. To find the molarity of the oxalic acid solution, we proceed as follows ... 

Citric acid (H3Cit) can be used as a household cleaning agent to dissolve rust stains. The rust, represented as Fe(OH)3, dissolves because the citrate ion forms a soluble complex with Fe3+ ... 

Because Fe(OH)3 is very insoluble (Ksp = 2.6 X 10-39), it forms as soon as the pH rises above pH 2. The red-brown rust stains that you ve seen in sinks and bathtubs are due to air oxidation of Fe2+(aq) followed by deposition of hydrous iron(III)... 

Both Fe(CN)s 4 and Fe(CN)i may be shown, by magnetic measurements (Chap. 25) to be spin-paired type complexes, but most other complexes of Fe(II) and Fe(III), in which, the ligand fields are weaker, are spin free, Other important complexes of Fe(III) are the asymmetric Fe(C204)i 3 ion (formed in removal of rust stains with oxalic acid) and the very deep red Fe(SCN)2" ion. Although the intensity of color of the latter complex could scarcely have been predicted, it is interesting that the azide ion (which is the same shape and has the same number of valence electrons as the 8CN ion) forms a Fe(III) complex whose color is almost as deep. 

Rusty colored Rust stains on clothing and water porcelain plumbing,... 

Oxalic acid is often used to remove rust stains. Explain what properties of oxalic acid allow it to accomplish this task. 

The most common uses of oxalic acid are in tanning leather and removing rust and ink stains. In stain removal, it acts as a reducing agent (a substance that donates electrons to other substances) and is relied on by most dry cleaners for this purpose. Iron rust stains con-... 

Oxalic acid, (COOH)2, is used to remove rust stains and some ink stains from fabrics. A 0.1743-gram sample of impure oxalic acid required 39.82 mL of 0.08915 M NaOH solution for complete neutralization. No acidic impurities were present. Calculate the percentage purity of the (C00H)2. 

Rust stains can be removed from painted surfaces with a solution of oxalic acid, (COOH)2. Calculate the pH of a 0.050 M oxalic acid solution. 

Bleaching Why can t rust stains be removed with bleach ... 

Oxalic acid, H2C2O4, is sometimes used to clean rust stains from sinks and bathtubs. Explain the chemistry underlying this cleaning action. 

Aquene 212. [Leatex] Organic amino deriv. chelating ent fa iroi and otha polyvalent metal ions prevents rust stains a iron spots in peroxide bleach systems with tqjtical brighten-eis. 

Sodium dithionite Bleaching textiles, pulp and paper removing rust stains... 

Dithionites are useful in removing rust stains, and neutral citrate solutions of Na2S204 were used to remove iron corrosion products from objects recovered from the Titanic. 

USE In cleansing compds, oil-well drilling, water treatment, cheese emulsification, as general sequestering agent, to remove rust stains, as ingredient of one-fluid ink eradicators, in electrodeposition ol metals. 

In their review of lichens in metal-enriched environments, Purvis and Halls (1996) present a list of lichens reported as rust-stained on iron-rich rocks, and an additional list of lichens typical of rocks rich in iron sulfide. Iron and steel serve sometimes as substrates for lichens (e.g. Brightman and Seaward, 1977 Garty, 1993). Crustose lichens are often observed to grow on old cannons (Figs. 6 and 7). The cannons located along the shore in Normandy, France were put in their present position less than 60 years ago (Fig. 7). Measurements of the lichen surface on these substrate may provide information on the rate of growth of certain crustose species. 

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