浅析镀锌彩钢板附着力的问题

1、镀锌层彩钢板本身附着力不好；

2、镀锌层彩钢板内混入气体，烘烤时发生膨胀，造成涂膜脱落；

3、热镀锌层较厚，锌层晶粒较粗，干扰磷化膜正常形成；

4、因锌层AL溶解，镀锌层彩钢板AL3+在磷化槽中积聚，使磷化膜结晶粗；

5、金属锌活性强，反应性强，使涂层粘度下降；

6、锌的二次生成物<碱式复盐〉镀锌层彩钢板易溶于水，喷涂时及烘烤时，透过涂层的水与底材上的盐类发生溶解反应，影响附着力；

7、锌因比如微电池作用，产生锈蚀产物，使体积膨胀，影响附着力；

8、锌在PH值为9-11时比较稳定，小于或大于此范围，锌溶解析出，影响附着力；

9、锌与涂层中的脂肪酸反应生成可溶解于水的金属皂盐，使涂层发脆或剥离；

10、镀锌后表面过于光滑，粗糙度不够，使涂漆附着力降低。

做镀锌喷涂，工序是先钝化，酸洗磷化，表面清理，喷涂底漆，喷涂面漆。这几个步骤都是必须的，任何一步做的不好都会影响粉末或油漆等涂层的附着。

镀锌后钝化和不钝化都产生喷涂后结合力不良的问题，因为钝化所产生膜层是含水的，不钝化就产生锌氧化问题，这两个问题都会产生喷涂后结合力不良，解决的办法是镀锌后磷化或陶化然后喷涂。

1、要求镀锌厂镀锌完毕不做钝化处理；

2、镀锌完毕后24小时内开始涂装；

3、喷涂前使用P80-120砂纸进行粗打磨，表面砂毛即可（必须使用气动打磨机，电动工具切削能力过大）；

4、适当作前处理（我们采用的是超声清洗脱脂、磷化处理）很牢

热浸镀锌质量好的话，会使底材合金化。如果是碳钢，从表面层往里做横切面的话，应该是：100%锌----锌96%+铁4%的合金---90%锌+10%铁的合金---75%锌+25%铁的合金

. The adhesion of zinc coating is not good;
2. When the gas is mixed into the zinc coating, it will expand during baking, resulting in the film falling off;
3. The results show that the zinc coating is thick and the grain size of zinc coating is coarse, which interferes with the normal formation of phosphating film;
4. Due to the dissolution of Al in zinc layer, Al3 + accumulates in phosphating bath, resulting in coarse crystallization of phosphating film;
5. Zinc has strong activity and reactivity, which reduces the viscosity of the coating;
6. The secondary product of zinc basic double salt is easily soluble in water. During spraying and baking, the water passing through the coating reacts with the salts on the substrate, which affects the adhesion;
7. Zinc, for example, due to the effect of micro battery, produces corrosion products, which makes the volume expand and affects the adhesin;
8. When the pH value is 9-11, zinc is relatively stable, less than or greater than this range, zinc dissolves and precipitates, affecting the adhesion
9. Zinc reacts with the fatty acid in the coating to form a metal soap salt which can be dissolved in water, making the coating brittle or peeling;
10. After galvanizing, the surface is too smooth and the roughness is not enough, which reduces the adhesion of painting.
Do galvanizing spraying, the process is passivation, pickling phosphating, surface cleaning, spraying primer, spraying finish. These steps are necessary, any step will affect the adhesion of powder or paint coating
Both passivation and non passivation after galvanizing have the problem of poor adhesion after spraying. Because the film produced by passivation contains water, non passivation will produce zinc oxidation problem. These two problems will produce poor adhesion after spraying. The solution is phosphating or ceramic after galvanizing and then spraying.
1. No passivation is required after galvanizing;
2. Start painting within 24 hours after galvanizing;
3. Before spraying, use p80-120 sandpaper for rough grinding, and the surface can be sanded (pneumatic grinder must be used, and the cutting capacity of electric tools is too large);
4. Appropriate pretreatment (we use ultrasonic cleaning degreasing, phosphating treatment) is very firm
If the quality of hot-dip galvanizing is good, the substrate will be alloyed. If it is carbon steel, the cross section from the surface layer to the inside should be: 100% zinc -- 96% zinc + 4% iron alloy -- 90% zinc + 10% iron alloy -- 75% zinc + 25% iron alloy