Cold galvanizing, also called electric galvanizing, is the use of electrolytic equipment to remove oil, pickling, after the pipe into the composition of zinc salt solution, and connected to the negative electrode of the electrolytic equipment. A zinc plate is placed on the opposite side of the pipe fitting, connected to the positive electrode of the electrolytic equipment to turn on the power supply, and a layer of zinc is deposited on the pipe fitting by the directional movement of the current from the positive electrode to the negative electrode.
Cold galvanizing is in the plating tank through the current unidirectional zinc gradually plated on the metal appearance, the production speed is slow, the coating is uniform, the thickness is thin, usually only 3-15 microns, the appearance is bright, smooth, high aesthetics, poor corrosion resistance, generally a few months will rust. Hot dip galvanized coating is thicker, generally 30-60 microns, coating corrosion resistance is higher. Suitable for outdoor work of steel parts, such as highway fences, power towers, large size fasteners and other more “rough” workpiece long-term rust prevention.
The surface of hot-dip galvanized steel wire is smooth, smooth, no cracks, joints, thorns, scars and rust, the galvanized layer is uniform, strong adhesion, corrosion resistance, toughness and elasticity are excellent. The tensile strength should be between 900Mpa-2200Mpa (wire diameter Φ0.2mm-Φ4.4mm). The number of twists (Φ0.5mm) is more than 20 times, and the repeated bending should be more than 13 times. Electrogalvanizing thickness is thin, usually only 3-15 microns, the appearance is bright, smooth, high aesthetics, poor corrosion resistance, generally a few months will rust.
There are solid particles in the plating solution when galvanizing, and if the edge and place of the parts are rough, it may be that the current density is too large. If the galvanized layer is good, but when the light comes out in 3% nitric acid, there is a black shadow on the coating, and the film layer appears brown when passivated, which may be that there are foreign metal impurities such as copper or lead in the galvanized liquid. First check the temperature and current density, and then through the plating solution analysis, determine and adjust the content of zinc and sodium hydroxide in the plating solution, whether the DPE content is low.
If the galvanized iron wire coating rough is not caused by the above reasons, it may be caused by impurities in the plating solution, you can take a small amount of plating solution, after filtration test, and then take a small amount of plating solution, after zinc powder treatment test, check whether the fault is caused by solid particles or copper, lead and other metallic impurities, one by one test, the cause of the fault is not difficult to find. Incomplete oil removal or excessive acid corrosion will cause foaming of the coating.
However, the main reason why this type of bath is easy to bubble is that the adsorption of organic additives on the coating crystal surface, so that the original crystal or some crystal faces can not grow normally, resulting in the development of new crystal nuclei or some crystal faces. Or the attachment of organic additives in the coating obstructs the normal arrangement of the lattice, causing lattice distortion, thereby increasing the internal stress of the coating, resulting in coating foaming. Clear the work area and equipment of all tools and piles that hinder activities.
Post time: 21-07-23