Steel polymer coatings

Biocorrosion of stainless steel is caused by exopolymer-producing bacteria. It can be shown that Fe is accumulated in the biofilm [2.62]. The effect of bacteria on the corrosion behavior of the Mo metal surface has also been investigated by XPS [2.63]. These last two investigations indicate a new field of research in which XPS can be employed successfully. XPS has also been used to study the corrosion of glasses [2.64], of polymer coatings on steel [2.65], of tooth-filling materials [2.66], and to investigate the role of surface hydroxyls of oxide films on metal [2.67] or other passive films. 

If the rf source is applied to the analysis of conducting bulk samples its figures of merit are very similar to those of the dc source [4.208]. This is also shown by comparative depth-profile analyses of commercial coatings an steel [4.209, 4.210]. The capability of the rf source is, however, unsurpassed in the analysis of poorly or nonconducting materials, e.g. anodic alumina films [4.211], chemical vapor deposition (CVD)-coated tool steels [4.212], composite materials such as ceramic coated steel [4.213], coated glass surfaces [4.214], and polymer coatings [4.209, 4.215, 4.216]. These coatings are used for automotive body parts and consist of a number of distinct polymer layers on a metallic substrate. The total thickness of the paint layers is typically more than 100 pm. An example of a quantitative depth profile on prepainted metal-coated steel is shown as in Fig. 4.39. 

Improvements in process and quality control made significant contributions to the transition from iron to steel as the major ferrous construction material over a century and a half ago. For most of that time red lead was relied upon, and not without a remarkable degree of success, as the rust-inhibitive pigment in anti-corrosive paints. In the last twenty years, however, there has been a similar dramatic change from such simple paints as red lead to synthetic polymer coatings which have as complex a technology as steel manufacture itself. 

Baudoin etal. [168,169] first presented qualitative depth profiles of lacquer and polymer coatings by means of r.f. GD-OES. Quantitative depth profiles were successively obtained by Payling et al. [170] on prepainted metal coated steel. Samples comprised a (rutile) pigmented silicone-modified polyester topcoat over a polymer primer, on top of an aluminium-zinc-silicon alloy coated steel substrate. With GD-OES in r.f. mode, it was possible to determine the depth profile through the polymer topcoat, polymer primer coat, metal alloy coating, and alloy layer binding to the steel substrate with a total depth of 50 im, all in about 60 min on the one sample. GD-OES depth profiles of unexposed and weathered silicone-modified polyesters were also reported [171]. Radiofrequency GD-OES has further been used to... 

Electrophoresis of water solutions of these salts and using steel as either the anode or the cathode, respectively, liberates the water-insoluble polymer coating through the reaction ... 

New Methods in Electrochemical Assessment of Polymer Coatings on Steel... 

The use of the impedance technique in the study of polymer coated steel, has been thoroughly described elsewhere. The present paper compares this technique with that of harmonic analysis, originally proposed by Meszaros ). The authors have presented preliminary data using the latter technique(3) wherein the early stages of polymer breakdown have been studied. The current paper extends this work to polymers which have been immersed for a considerable period of time. The harmonic method gives information not available from the impedance technique in the Tafel slopes and the corrosion current are directly measurable. A brief summary of the harmonic method and the equations used are given below. 

Polymer coatings on stiffer substrates can be measured by time-resolved techniques (Sinton et al. 1989). Often in these cases it is not convenient to measure a direct reflection from an uncoated part of the substrate at more or less the same time, and anyway the substrate may not be flat, but this may not matter if it can be assumed that either the thickness or the longitudinal velocity of the coating does not vary. The time interval between the echoes from the top and bottom surfaces of the coating can then be used to determine the unknown quantity. An example of the kind of signal that can be obtained is shown in Fig. 10.5. The specimen was a coating of PET (polyethylene terephthalate) 15 m thick on a stone-finish rolled steel substrate. Although there is some overlap of the two echoes, there is no difficulty in... 

SPME uses a polymer-coated fused-silica fiber, typically 1 cm 100 m, that is fastened into the end of a fine stainless steel tube contained in a syringelike device and protected by an outer stainless steel needle. In use, the plunger of the device is depressed to expose the fiber to the sample matrix so that the organic compounds to be sorbed onto the fiber. The plunger is retracted at the end of the sampling time, and then it is depressed again to expose the fiber to a desorption interface for analysis typically by GC or LC. In a recent variation of this technique, the so-called in-tube SPME, the polymer is not coated on a fiber but on the inside of a fused-silica capillary before analysis by LC. 

Cold-rolled steel panels were purchased from Advanced Coating Technologies, Inc. (Hillsdale, Michigan). Silane chemicals (methylsilane, trimethylsilane, and tetramethylsilane) were purchased from Petrarch Systems, Inc. The silane plasma-deposited steel was then dip-coated with a polymer film 10-25 pim thick. The polymer coating resins used were silane-modified polymers with functionalities such as hydroxyl, acrylate, or amine. 

Figure 8. Schematic diagram of coating on a zinc-phosphated steel substrate. Thin plasma polymer is first deposited on the phosphate crystal surface, followed by an organofunctional silane polymer coating.

In addition to metallic materials, ceramics such as SiC, Si3N4, AI2O3, and mullite are also materials that will most likely perform well under the harsh S-I environment, and their applicability should be explored. Since the temperature does not exceed I20°C in Section I, fluoro-polymer coatings such as Teflon or glass-lined steel can also be viable options. The choices will depend more on the application. 

Rustmaster is a water-based polymer formulation that prevents corrosion in two different ways. First, the polymer layer that cures in air forms a barrier impenetrable to both oxygen and water vapor. Second, the chemicals in the coating react with the steel surface to produce an interlayer between the metal and the polymer coating. This interlayer is a complex mineral called pyroaurite that contains cations of the form [M1 xZr(OH)2]x+, where... 

Parylene N to smooth surface materials has been reported with the application of plasma depositions [13,14]. It was reported that excellent adhesion of Parylene C coating to a cold-rolled steel surface was achieved using plasma polymer coatings, in turn giving rise to corrosion protection of the metal [15]. Another major deficiency of Parylene C is its poor painting properties when paint is applied on a Parylene C film, due to its extremely hydrophobic surface. Because of this, surface modification of Parylene films is necessary to enhance their adhesion performance with spray primers. 

TMS plasma polymer coated steels were analyzed by SNMS. This analytical technique permitted obtainment of high resolution and quantitative information... 

The effect of interface of steel on the corrosion test result is summarized in Table 33.2. The results found for the panels, which were E-coated without phosphate or plasma polymer coatings, are quite astonishing. A scribe creep of 3.0 mm in a 4-week corrosion test was obtained for an oxide-removed CRS surface (without zinc phosphate nor plasma polymer), which is better than the E-coat on the... 

All experimental data and discussions presented above seem to confirm the validity of the hypothesis that if reducible elements present in the surface state (including the ultrathin layer of plasma polymer) on which a cathodic E-coat is applied, those elements will be subjected to the cathodic reduction during the process of the cathodic E-coat deposition, and a weak boundary or defective spots would be created in the interface of the E-coat and the substrate (plasma polymer-coated steel). The validity of the hypothesis implies that the best result of a cathodic E-coat cannot be realized unless the adverse effect of the cathodic reduction can be minimized. In this context, the presence or absence of oxides is a very important factor in the use of a cathodic E-coat, besides the fact that the presence of oxides... 

Consider a 0.25 cm radius steel disk covered with a polymer coating that has a thickness of 100 im. The electrolyte is a 0.1 M NaCl solution at room temperature. Estimate the frequency above which geometry-induced time-constant dispersion will influence the impedance response. 

Pigmented polymer coatings on steel and PTFE as well as PTFE-based copolymers can be analyzed by rf-GD-MS in order to fingerprint them [648]. Advantages compared with SIMS and x-ray photoelectron spectroscopy are that the method is fast and does not require dissolution of the sample, and thermal volatilization processes do not appear to take place. 

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