Resistivity surface treatments

Approaches for the development of water-resistant surface treatments include application of inhibitors to retard the hydration of oxides or the development of highly crystalline oxides as opposed to more amorphous oxides. Standard chemical etching procedures, which remove surface flaws, also result in improved resistance to high humidity. 

Dyna-BIue, Wear-resistant surface treatment. Dynamic Metal Treating, Inc. 

Chromium is used extensively for (1) manufacture of stainless steels, (2) decorative and wear-resistant surface treatments, and (3) manufacture of chemicals. 

Chignsa H., Abe M., Aoki K., Fukazawa K. Color display tnbe with a high-contrast and a low surface resistivity surface treatment against the alternating electric field. Technical Report of lElCE. EID96-33 (1996-07), pp. 1-6... 

Corrosion. Ammonium bifluoride dissolves in aqueous solutions to yield the acidic bifluoride ion the pH of a 5% solution is 3.5. In most cases, NH4HF2 solutions react readily with surface oxide coatings on metals thus NH4HF2 is used in pickling solutions (see Metal surface treatments). Many plastics, such as polyethylene, polypropylene, unplasticized PVC, and carbon brick, are resistant to attack by ammonium bifluoride. 

Metal Treatment. After rolling, the oxide scale on sheet steel is removed by acid treatment (pickling) (see Metal surface treatments). Phosphoric acid, a good pickling agent, leaves the steel coated with a thin film of iron phosphates. This process improves mst resistance but presents a problem if the steel is to be electroplated. 

Plasma processing technologies ate used for surface treatments and coatings for plastics, elastomers, glasses, metals, ceramics, etc. Such treatments provide better wear characteristics, thermal stability, color, controlled electrical properties, lubricity, abrasion resistance, barrier properties, adhesion promotion, wettability, blood compatibility, and controlled light transmissivity. 

To produce wear-resistant or hardened surfaces, thin layers of borides can be prepared on metal surfaces by reaction and diffusion (see Metal SURFACE treatments). Boride powders can be formed iato monolithic shapes by cold pressing and sintering, or by hot pressiag. 

Electroplating. Chromium is electroplated onto various substrates in order to realize a more decorative and corrosion- or wear-resistant surface (24—32). About 80% of the chromium employed in metal treatment is used for chromium plating over 50% is for decorative chromium plating (see Metal surface treatments). Hard chromium plating differs from decorative plating mostiy in terms of thickness. Hard chromium plate may be 10 to several 100 p.m thick, whereas the chromium layers in a decorative plate may be as thin as 0.25 p.m, which corresponds to about two grams Cr per square meter of surface. 

CAA. Chromic acid anodization [74-76]. was developed initially as a treatment to improve the corrosion resistance of aluminum surfaces, but it is also used as a surface treatment for adhesive bonding especially in Europe where it is used extensively in aerospace applieations [29,77],... 

Primers are required to be resistant to all of the same fluids and environments as the adhesive, and are in addition expected to be compatible with secondary finishes such as corrosion and fluid resistant primers applied to cured bond assemblies. The most commonly used primers for 250°F cured epoxy adhesives also have active corrosion inhibitors themselves to combat corrosion at bondlines. This last requirement is somewhat dated, evolving from the severe corrosion and delamination problems experienced before U.S. airframe manufacturers adopted durable surface treatments. 

In-service issues. As mentioned previously, many early service failures of bonded structure were due to adherend surface treatments that were unstable in long-term exposure to water. A majority of these problems were resolved by the adoption of surface treatments such as chromic and phosphoric acid anodize for aluminum details. The remaining few were alleviated by the adoption of phosphoric acid anodized honeycomb core and foaming adhesives resistant to water passage. Other service durability issues such as the cracking of brittle potting compound used to seal honeycomb sandwich assemblies, and subsequent delamination, have been minor in scope. 

Jones, R. D. and Jones, D. P., Hot-dip Aluminized Steel Strip for Corrosion Resistant Applications , in Surface Treatment for Corrosion and Wear Resistance, Strafford, Datta and Googen (eds), Ellis Horwood, Chichester (1984)... 

In the flat/container glass fields a wide range of surface treatments now exist which modify the surface of the glass to confer corrosion or abrasion resistance, improve mechanical strength or optical properties. A number of treatments which claim to improve chemical or corrosion resistance are described in References 31 to 35. 

When the test is to be made to predict the performance of a material in a particular service, the ideal procedure would be to have the surface of the test-pieces duplicate the surface of the material as it would be used. Here, however, a complication is presented by the fact that materials in service are commonly used in several forms with different conditions of surface. Where the number of materials to be compared is large, it will usually be impractical to test all the conditions of surface treatment of possible interest. The best practical procedure, then, is to choose some condition of surface more or less arbitrarily selected to allow the materials to perform near the upper limits of their ability. If all the materials to be tested are treated in this way, and preferably with uniform surface treatment, the results of the test will indicate the relative abilities of the different materials to resist the test environment when in a satisfactory condition of surface treatment. Then, if it should be considered prudent or desirable to do so, the most promising materials can be subjected to further tests in a variety of surface conditions so that any surface sensitivity can be detected. 

Since most fabricated products are attractive as well as inherently corrosion and rust resistant when fabricated they usually do not require any finishing or decoration. For others there are paints, coatings, and other surface treatments that usually are used mainly to enhance eye appeal. Tables 8-35 to 8-37 provide some guidelines. 

Alternatively because of the degree to which it both reflects white light and absorbs in the ultraviolet, it may inhibit photodegradation. Which of these two possibilities predominates depends on a variety of factors including the concentration of the TiOj pigment used, the nature of any surface treatments, and the extent to which the polymer itself is able to resist photodegradation. 

---