Anodizing quality control

The quality control of galvanic anodes is reduced mainly to the analytical control of the chemical composition of the alloy, to the quality and coating of the support, to an adequate joint between support and anode material, as well as to restricting the weight and size of the anode. The standards in Refs. 6, 7, 22, 27, 31 refer to magnesium and zinc anodes. Corresponding specifications for aluminum anodes do not exist. In addition, the lowest values of the rest potentials are also given [16]. The analytical data represent the minimum requirements, which are usually exceeded. 

For these reasons alloying elements appear in all the commercial anodes, and very careful quality control is required to keep disadvantageous tramp elements (notably iron and copper) below defined threshold levels. Many anode failures can be attributed to poor production quality control. A guide to minimum quality standards has been produced ... 

Alloying additions are made to improve the performance of an anode material. Of equal importance is the control of the levels of impurity in the final anode, since impurities (notably iron and copper) can adversely affect anode performance. Thus careful quality control of the raw materials used and the manufacturing process adopted is essential to sound anode production. This too is discussed below. 

Tests of sacrificial anode materials are generally conducted for three reasons for screening (or ranking), performance information and quality control. 

Quality control tests are intended to detect produced materials which deviate from manufacturing specifications, and thus may result in questionable performance. The materials are usually subjected to spectrographic analysis which is the primary quality control check. The exposure tests are necessarily of short duration (hours or days), in which the test conditions attempt to reflect the environment of operation, for example using artificial seawater for a marine application. Since a property that is reproducible and indicative of a consistent quality anode is all that is required, there is no attempt to mirror, except in the crudest fashion, current density profiles. 

Screening methods for Water data InFormaTion in support of the implementation of the Water Framework Directive Water Framework Directive Screening Methods/Emerging Tools Enzyme-Linked ImmunoSorbent Assays Quality Control/Quality Assurance Square Wave Anodic Stripping Voltametry... 

EIS and other electrochemical methods appear to be useful for the study of the performance of metal pretreatments (cleaning processes, anodization, phosphating, chro-mating, etc.) prior to adhesive bonding. A quick comparison of methods can be achieved, and because the method is fast and straightforward, it can be used as a quality control method. On adhesively bonded system EIS could be performed in more fundamental studies that would provide information on the nature and locus of degradation processes, when immersed in aggressive solutions. 

Routine analytical methods typically include micro (graphite furnace) atomic absorption spectrometry and electrochemical approaches such as anodic-stripping voltammetry. More complex, expensive and nonroutine/ research approaches are inductively coupled plasma-mass spectrometry and definitive methods such as thermal ionization-mass spectrometry. These methods have the requisite sensitivity, specificity, and record of reliability for quantification across the range of environmental exposures that humans presently encounter. Combining current instrumental methods with carefiil quality assurance and quality control protocols permits adequate proficiency for even low Pb concentrations, values of 1—2 pg/dl. 

Soaking three spraycoated Y2O3 on anodized aluminum in 3.5wt% NaCl solution for 7 days, the EIS data are shown in Fig.29. The EIS data indicate that samples coated at different time have the similar overall impedance and the quality control of coating process is consistent. The complete analysis of the EIS data using a three-time constant interface model is shown below (Table 7). 

For a more economical fabrication of microtubular SOFC with more reliability and flexibility in quality control, an advanced dry-jet wet extrusion technique, that is, a phase inversion-based co-extrusion process, followed by co-sintering and reduction processes was employed to fabricate a novel electroly te/anode dual-layer hollow fiber. Using the co-extrusion technique, one of the layers has to be thick in order to provide mechanical strength to the fiber, and in this design, the anode is chosen to be the thick layer due to the much lower ohmic losses (as shown in Figure 11.16). Use of co-extrusion has many advantages over conventional dry-jet wet extrusion methods such as simplified fabrication and better control over the manbrane structure. Furthermore, the risk of defects formation can be reduced and at the same time greater adhesion between the layers can be achieved. 

The constituent elements of anode materials, other than the basis metal, are present whether as a result of being impurities in the raw materials or deliberate alloying additions. The impurity elements can be deleterious to anode performance, thus it is necessary to control the quality of the input materials in order to achieve the required anode performance. Since this will usually have an adverse impact on costs it is often desirable to tolerate a level of impurities and to overcome their action by making alloying additions. Alloying elements may also be added for other reasons which are important to anode production and performance. These matters are discussed in this section. 

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