What are the factors related to the tightness of the inner coating and the tube?
The type of heating equipment,heating method,fuel type,heating temperature,fineness of plastic powder,additive composition,etc.will all have a certain impact,but the key is still the external pretreatment. Under the premise that the appearance pretreatment is qualified,the comprehensive target is checked by adhesion,and China’s specifications are now close to developed.
However,these measures can not completely eliminate the problem of coating fall,the reasons are as follows:
1. The galvanized steel pipe and the welded steel pipe are heated in the heating furnace. Because the galvanized steel pipe has an extra layer of galvanized layer,the galvanized layer has a reflection effect on heat. In addition,the galvanized layer strengthens the surface finish of the steel pipe and reduces the heat absorption. Therefore,the coating effect of the galvanized steel pipe as the base pipe is not as good as that of the welded steel pipe.
2.There is a bad practice of adding an adhesive in the additive.According to industry experts,a certain adhesive is incorporated in the plastic powder,which can firmly adhere the coating to the wall of the steel pipe after the compounding process. The adhesion target can be completely qualified,but the adhesive has an expiration date.
Once the expiration date (usually three months) ,the coating will fall,which will block the water flow channel and cause an accident. The consequences will be serious. The result is that the reputation of plastic-coated steel pipes is gradually being replaced by plastic-lined steel pipes. Therefore,to truly solve the quality problems of plastic-coated steel pipes,we must rely on the brand and eliminate bad products.