中文版Screw corrosion prevention processing (one) foreword
Foreword
The metal receives the environment the influence, affiliation chemistry or the electrochemistry responded that creates the destructive violation, is called the corrosion, the nearly all metal product, in certain environment, will have corrosion of phenomenon certain state, but the screw will be the metal product, when the nature avoidless metal corrosion's question, its use's environment and the time will be different, will corrode the phenomenon will also have the obvious difference. Many pollutional industry, like the steel and iron, the petrochemical, the thermoelectricity generation and so on, the steam, the locomotive grew largely in recent years in addition, the massive emissions's waste gas, caused in the air to fill sulfide and the nitride gas and the particle the corrosive, these were create the metal corrosion the primary cause. For example Formosa Plastics Group six light Mai Liaochang, at present metal corrosion situations and so on discovery screw, bolt, structural steel and pipeline, before its gravity possible to have surpassed puts up a factory originally, the estimate, forms question which the project personnel must take seriously and first solve.
The metal corrosion can create the large amount maintenance of equipment cost and the serious economic loss, if because of corrodes increases the design, the manufacture, the maintenance and the maintenance cost, or even has the harm and the disaster. use scope is most widespread, quantity demand is also biggest, fit and unfit quality of its resistance to corrosion decided that durability of its use, has the major impact on security and the reliability the equipment, therefore the research corrosion prevention method, the development and the application modern corrosion prevention technology, is the current important topic.
Corrosion prevention method
The metal anticorrosion's method mainly has four of aspects, namely control material itself, design of use environment, material and the environment contact surface and the improvement metal structure, if uses the complete corrosion resistance the alloy to make the screw, only if has needs specially, otherwise says in the economical viewpoint is impractical, or attending produces screw's surface the corrosion environmental factor to isolate completely, not necessarily is also accepted in the practice, possibly is difficult. The improvement metal structure design may get down influence of the improvement special condition in some kind of situation, but designs of the most screw are unable the sufficient share revision, and its protective function also non-permanence, therefore this law cannot basic solve the problem, only then on the contact surface the corrosion prevention, i.e. superficial corrosion prevention processing applies the most widespread method at present.
Superficial corrosion prevention processing is refers to utilizes each method to exert the protector in the metal surface, its function is the metal and the corrosive environment isolation, suppresses the corrosion process the production, or reduced corrosive medium and metal surface contact, but achieves prevents or the mitigate corrosion goal. The protector ought to be able to meet the following requirement: 1. anticorrosion, wear-resisting, high degree of hardness, 2. structure close, complete, the hole is small, 3. is reliable with the parent metal union, the cementing power is good, and 4. uniform distribution has certain thickness. The protector usually divides into the metal coating and the nonmetallic coating two kinds, the metal coating is refers to with the corrosion resistance strong metal or the alloy the metal surface which easy to corrode is forming the protector, this kind of coating is called coating. Has the metal clad method and the type are quite many, what is most common is the galvanizing process, next is the molten metal soaks plates the law (hot dipping to plate) and chemistry surface treatment.
The nonmetallic coating is refers to with the organic high polymer material like paint, and the inorganic material like ceramics, form the protector on the hardware or the components surface, this protector can isolates completely the parent metal and the ambient medium, prevents the parent metal to create because of the contact corrosion medium the corrosion.
