Protective Actions

All hydrophilic colloids possess some degree of protective action and gelatin, starch and casein are used commercially for this purpose. 

ERPG-2 The maximum airborne concentration below which it is believed that nearly all individuals coiild be exposed for up to one hour without experiencing irreversible or other serious health effec ts or symptoms that could impair their ability to take protective action. 

Surface films are formed by corrosion on practically all commercial metals and consist of solid corrosion products (see area II in Fig. 2-2). It is essential for the protective action of these surface films that they be sufficiently thick and homogeneous to sustain the transport of the reaction products between metal and medium. With ferrous materials and many other metals, the surface films have a considerably higher conductivity for electrons than for ions. Thus the cathodic redox reaction according to Eq. (2-9) is considerably less restricted than it is by the transport of metal ions. The location of the cathodic partial reaction is not only the interface between the metal and the medium but also the interface between the film and medium, in which the reaction product OH is formed on the surface film and raises the pH. With most metals this reduces the solubility of the surface film (i.e., the passive state is stabilized). 

Metal coatings are applied in special cases where the protective action has to be ensured by the coating metal or its corrosion products. Additional electrochemi-... 

For normally buried tanks, tanks with measures against buoyancy and tanks with a secondary containment, no difficulties are to be expected for protection current densities below 200 fJ.A m. On the other hand, the protective action can... 

With local cathodic protection, the off potential measurement cannot be used directly to check the protective action because, due to the mixed type of installation of the protected object and foreign cathodic structures in the soil, there is a considerable flow of cell currents and equalizing currents. The notes to Eq. (3-28) in Section 3.3 are relevant here, where the // -free potentials must be substantially more negative than the off potential of the protected object. If t/ ff is found to be more positive than U, this does not confirm or conclusively indicate insufficient... 

The protective action of alloying has been demonstrated by a series of investigations on stainless steels [35-37], titanium [38-40], lead [41.42], and tantalum [43]. 

Selfcare precautions mean exactly that. The rescuer must take self protective actions to keep from becoming another victim and thereby part of the problem rather than part of the solution. 

The antiadrenaline and antinoradrenaline activity of iV-benzyl-A -2 -halogenoethyl 2-thenylamines has been studied, " as has the radiation protective action of iV-phenylamidines of thiophenecarboxylic acid in white rats. ... 

With poor combustion, on the other hand, very severe acceleration of attack, dependent upon the formation of sulphide in the scale, can occur. This destroys the protective action of the scale, and results in sulphide penetration of the metal in advance of oxidation. The effect is illustrated by tests... 

Lead coatings are mainly applied by cladding and find principal use in the chemical industry for resistance to sulphuric acid, for cable sheathing resistant to attack by soils and in architectural applications where resistance to industrial atmospheres is particularly good. They rely for their protective action on the formation of insoluble corrosion products which stifle the corrosion reaction and lead to very long service lives, but the corrosion resistance is impaired when chlorides are present. 

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