General corrosion

Alter the chemistry of the common fluid to render it less conductive and/or less corrosive. Generally, water corrosivity increases with an increase in temperature and oxygen content and a decrease in pH. Inhibitors may he effective. Note that in mixed-metal systems, higher dosages of inhibitors may be required than would be necessary in single-metal systems in the same environment. 

Erosion corrosion occurs in an environment where there is flow of the corrosive medium over the apparatus surface. This type of corrosion is greatly accelerated when the flowing medium contains solid particles. The corrosion rate increases with velocity. Erosion corrosion generally manifests as a localized problem due to maldistributions of flow in the apparatus. Corroded regions are often clean, due to the abrasive action of moving particulates, and occur in patterns or waves in the direction of flow. 

Effect of Crystal Defects on Corrosion—General Considerations... 

Uniform Corrosion (general corrosion) corrosion in which no distinguishable area of the metal surface is solely anodic or cathodic, i.e. anodes and cathodes are inseparable, cf. localised corrosion. 

General Etch Oxygen Corrosion (Uniform Rate Corrosion/General Wastage Corrosion)... 

Hydrogen embrittlement is commonly associated with problems of excessive waterside deposition in boilers operating at over 1000 psig. Where HE takes place, the primary form of corrosion generally is either ... 

The deposit of nickel on top of the copper provides the essential resistance of the system to corrosion. Generally it is deposited from a solution based on the familiar Watts formulation—300 g 1 1 nickel sulphate, 30 g 1 1 nickel chloride, and 40 g 1 1 boric acid—and as in the copper processes the solutions contain additives to help give a bright deposit with good levelling characteristics. 

Corrosion General corrosion, crevice corrosion, pitting, hydrogen damage, caustic corrosion, intergranular corrosion, microbiological corrosion... 

Corrosion General wastage, General or Path of penetration... 

The position of the water table determines the oxygen transport and hence the corrosion rate. The moisture content of soil greater than 20% is deemed to be corrosive (general corrosion of carbon steel) and the value of less than 20% was conducive to pitting corrosion.15 This observation is thought to be related to the diffusion rate of oxygen.16 The general effect of soil resistivity on the corrosivity may be denoted as ... 

Erosion-corrosion. Generally, all types of corrosive media can cause erosion-corrosion, including aqueous solutions, organic media, gases, and liquid metals. The corrodent can be a bulk fluid, a film, droplets or a substance adsorbed on or absorbed on another substance. For example, hot gases may oxidize a metal at high velocity and blow off an otherwise protective scale. Solid suspensions in liquids (slurries) are particularly destructive from the standpoint of erosion corrosion.16 31... 

No Corrosion General Galvanic Erosion Crevice iW.MirVV. ... 

I) Pug i corrosion, general services uiut storage fuciliiieu account for 60% of buttery limits fnvcutnumfu an a first approximation. 

Metals corrode by an electrochemical reaction where metal loss occurs as oxidation at the anode sites and plating out occurs at the cathode. This phenomenon manifests in two distinct ways general corrosion or localized corrosion. General corrosion refers to a uniform loss of the metal thickness due to the interaction of the metal and the chemical to which... 

Electrochemical processes occur in batteries, fuel cells, electrolysis, electrolytic plating, and corrosion (generally an undesirable process). Electrochemical processes can be used to produce electricity, to recover metals from solution, and for the measurement of the thermodynamic properties of electrolyte solutions. The device used to study electrochemical reactions is an electrochemical cell, which consists of two electrodes (metallic conductors) in electrolytes that are usually liquids containing salts, but may be solids, as in solid-state batteries. The two electrodes may be in the same electrolyte, as shown in Fig. 14.6-la, or each electrode may be in a separate compartment wiffi its... 

CORROSION, GENERAL - A form of deterioration that is distributed more or less uniformly over a surface. 

CORROSION, IMPINGEMENT - A form of eroslon-corrosion generally associated with local impingement of a high velocity, flowing fluid against a solid surface. 

For nongalvanized steel, cosmetic corrosion generally involves a cathodic delamination mechanism the surface under the paint becomes cathodic and the surface exposed in the hole becomes anodic. To slow down or prevent atmospheric corrosion, it is therefore important that the siuface treatment be a good cathodic inhibitor in the finished product. The phosphate layer increases corrosion resistance by limiting the available free surface for the cathodic reaction. In general, the activity of the free surface is further reduced by passivating posttreatments or by the deposition of amorphous phosphate films between the crystals. 

---