Weathered surface

While the continual removal of atmospheric pollution by rain washing is beneficial, the removal of the protective corrosion product is obviously undesirable. The retention of the weathered surface is therefore usually preferred unless aesthetic considerations are of major importance, in which case abrasive or specialist chemical cleaning are effective. 

Duncan, J. R., Electron Spectroscopy of Chromated Galvanized Steel Sheet after Heating. Immersion in Water or Outdoor Weathering. Surface Tech., 17, 265-276 (1982)... 

Sport - advanced composite materials for tennis and squash rackets, all-weather surfaces. 

Intervals between application and sampling of apples retaining weathered surface residues of parathion ranged between 21 and 70 days. At harvest, these residues were 0.05 p.p.m. or less, following each of 13 varied schedules of application (Table III). (These values are derived from samples containing an optimum amount of parathion for analytical precision.) Low level surface residues on apples were not carried over as ultimate residues in cider (Table III). This fact supports the contention that there is close association of the parathion deposits with the waxlike coating of the fruit. 

Freshly cast lead has a bright, silvery appearance. On exposure to the atmosphere, however, lead in the surface layer combines with atmospheric oxygen and carbon dioxide to form a dark, stable gray coating of mixed lead oxide and basic lead carbonate. This layer usually protects the metal from further oxidation and corrosion (see Fig. 38). Protected by a weathered surface layer, solid lead is stable to further corrosion. Lead is also very ductile and soft, being the softest metal known in antiquity. It is mainly because of these properties that lead was widely used for building, to make pipes and roofs, and in naval construction, for example. Solid lead flows, albeit very... 

Surface Preparation of the Substrate. This is extremely important for all methods of paint and coatings application. The failure of a paint system is often due not to the paint itself, but because of a failure in surface preparation. For example, an anticorrosive paint applied to a rusty surface will not be effective if the rust falls off taking the new paint with it. For wood and plastic surfaces, old paint or a weathered surface layer may have to be removed. For older metal objects, the removal of corrosion is often required. Sandblasting is one method to remove both the old paint and any corrosion. For new metal objects, a phosphate or chromate layer is often chemically bonded to the metal to provide a surface to which a coating can easily adhere. 

Manganese is mainly present as manganese (II) carbonates, but in some sediments and on weathering surfaces it is present as higher oxides such as manganite and pyrolusite. In some pelagic sediments the amount... 

In the presence of aerated water, the oxidation of arsenopyrite is relatively rapid and its arsenic oxidizes faster than its sulfide (Foster, 2003), 37. During oxidation, As1- and As0 on the surfaces of the arsenopyrite initially convert to As2+, As3+, As5+, and possibly As1+ (Nesbitt, Muir and Pratt, 1995 Schaufuss et al., 2000). Scorodite (FeAs04-2H20) or amorphous Fe(III) arsenates commonly precipitate from the oxidation of arsenopyrite ((Krause and Ettel, 1988), 851 (Williams, 2001), 273 (Craw, Falconer and Youngson, 2003), 73 Chapter 3). If any arsenic on the weathered surfaces of arsenopyrite dissolves into aerated water, the arsenic will exist as As(V) or As(III). Unless As(III) enters reducing environments, it will convert to As(V) over time (Chapter 3). 

Psilolechia leprosa Uncharacterized secondary copper minerals/beneath lightening conductors on churches Cu (uncharacterized weathered surfaces) Sweden, UK Purvis (1996)... 

To make any new copper sheets look like the old ones, the restorers transplanted the patina from a weathered piece of copper to the new surface. Applying acetone, an organic solvent, to the weathered surface and scraping with an abrasive cloth caused tiny flakes of patina to fall off. These flakes, applied to the new copper, attached themselves permanently in one to three weeks of exposure to the atmosphere. 

Figure 8. Weathered surface of softwood after 15 years of exposure (in Madison, Wisconsin).

Schwarz, T. Germann, K. (1999) Weathering surfaces, laterite-derived sediments and associated mineral deposits in north-east Africa. In Thiry, M. Simon-Coinf on, R. (Eds) Palaeoweathering, Palaeosutfaces and Related Continental Deposits. International Association of Sediment ologists Special Publication 27. Oxford Blackwell, pp. 367-390. 

Metastable crystalline microfibril —> crystalline interior -I- annealed/weathered surface. .. with a spacing of 1.043 nm —> 1.043 nm -I- 1.029 nm... 

Denmark. The government statistical department publishes annually statistics on population, weather, surface area, employment, housing, agriculture, industry (numbers employed in different branches), output of principal products (virtually no chemicals), fuel and power supplies, transport, consumption of food and staple commodities, cost of living, wholesale and retail prices, public finance, social insurance, and education. This publication (11) is in French as well as Danish. 

Comparisons of time-scales for various physical processes have been discussed by Lerman (1979) and Schwartzenbach and Imboden (1984). In general, physical processes in lakes have characteristic times in the range of 10 to 10 years. Oceanic processes span times from days to thousands of years (Broecker, 1974) and geological events may occur catastrophically (e.g. earthquakes or landslides exposing new weathering surfaces) or very slowly. 

Most soil reactions occur at the soil solution/soD interface. Ions in water can move and react fast enough to measure easily. Slower but still measurable reactions occur in the weathered surfaces of soil particles. These poorly understood surfaces contain considerable water. Reaction rates in the truly solid phase at soil temperatures, however, are too slow to be measured in our lifetimes. 

The concentration of A1 hydroxide in soils is usually high enough that Eq. 3.45 is adequate and Eq. 3.46 is unnecessary. That is probably not true for ions in trace concentrations in soils. The mole fraction concentrations of phosphate and transition metal ions in soils are <3C0.01. So soil phosphate solubility at equilibrium can be orders of magnitude less than the solubility of pure A1 phosphate, as many soil measurements show. We can call it equilibrium because the solubility changes slowly to imperceptibly with time. If anything, the aqueous phosphate concentration decreases with time as the surface A1 ions slowly diffuse into the weathered surface, mix further with other ions, and further increase their entropy. Simple AIPO4 solubility product equivalent to Eq. 3.45, on the other hand, predicts that the phosphate concentration will increase with time. 

In the weathered surfaces of soil particles where some semiliquid water may be present, ion diffusion may be fast enough to affect laboratory and field experiments. The slow removal of phosphate ions by soils from the aqueous phase may be due to the slow diffusion of PO4 to A1 and Fe ions within the weathered surface. The increasing strength of trace metal retention by soils with time may similarly be due to such diffusion into the semisolid, weathered surfaces of soil particles. 

For inorganic ions, the reactions themselves can be very fast, but the ions may have to diffuse through soil pores before they reach a reaction site. The ions may also have to diffuse through the weathered surface. Diffusion processes lend themselves to kinetic treatment. With multiple diffusion and reaction processes going on simultaneously, the kinetic treatment can become very complex. 

Flexibility at low temperatures Coefficient of friction Stability at high temperatures Dielectric constant Dissipation factor Arc resistance Volume resistivity Surface resistivity Insolubility Chemical resistance Weatherability Surface energy Flame resistance... 

Certainly the environmental history of use and method of fabrication of an object will influence its environmental interaction. Weathered surfaces, the orientation of the tissue on the exposed surfaces, mechanical damage from pounding or stress, and changes caused by heating will influence the degradation patterns. 

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