Tag: powder coating pretreatment
Filiform corrosion is appearing mostly on aluminum
Filiform corrosion is special kind of corrosion appearing mostly on aluminum. The phenomenon resembles a worm creeping under the coating, always starting from a cut edge or a damage in the layer. Filiform corrosion develops easily when the coated object is exposed to salt in combination with temperatures 30/40°C and relative humidity 60-90%. This problem is therefore limited to coastal areas and linked with unfortunate combination of aluminum alloys and pre-treatment. To minimize filiform corrosions it is advised to ensureRead More …
Chemical surface preparation before powder coating
Chemical Surface Preparation Particular application is closely related to the nature of the surface being cleaned and the nature of the contamination. Most surfaces powder coated after cleaning are either galvanized steel, steel, or aluminum. Since not all chemical-type preparations are applicable to all these materials, the preparation process selected depends on the substrate material. For each material, the type of cleaning will be discussed and its unique features for that substrate will be explained. Specific application processes are quiteRead More …
Conversion Coating of Galvanized Steel
Iron phosphates or cleaner-coater products produce little or non-detectable conversion coatings on zinc surfaces. Many multimetal finishing lines use modified iron phosphates which offer cleaning, and leave micro-chemical etch on zinc substrates to provide adhesion properties. Many municipalities and states now have limits on zinc PPMs, forcing metal finishers to provide treatment of any solutions in which zinc substrates are processed. The zinc phosphate conversion coating is, perhaps, the highest quality coating that can be produced on a galvanized surface. ToRead More …
Definitions for corrosion classification
As an aid in finding what requirements should be made for pre-treatment, we can define different corrosion classification: Corrosion Class 0 Indoors with relative humidity over 60% Very little corrosion risk (aggressivity) CORROSION CLASS 1 Indoors in non-heated, well ventilated room Little corrosion risk (aggressivity) Corrosion Class 2 Indoors with fluctuating temperature and humidity. Outdoors in inland climates, far from sea and industry. Medium corrosion risk (aggressivity) CORROSION CLASS 3 In densely populated areas or near industrial areas. Above open waterRead More …
Phosphate Coatings Pretreatment for Steel Substrates
Phosphate Coatings Pretreatment for Steel Substrates The recognised pre-treatment for steel substrates just prior to application of powder is phosphating which can vary in coating weight. The greater the conversion coating weight the greater the degree of corrosion resistance achieved; the lower the coating weight the better the mechanical properties. It is therefore necessary to select a compromise between mechanical properties and corrosion resistance. High phosphate coating weights can give trouble with powder coatings in that crystal fracture can occurRead More …
Alkaline Acid Cleaners of CLEANING ALUMINUM
Cleaners of CLEANING ALUMINUM Alkaline Cleaners Alkaline cleaners for aluminum differ from those used for steel; they usually have a blend of mild alkaline salts to avoid attacking the aluminum surface. In some cases, a small to moderate amount of free caustic soda may be present in the cleaner to remove difficult soils, or to provide a desired etch. In the power spray method of application, the parts to be cleaned are suspended in a tunnel while the cleaning solutionRead More …
Paint Removal, How To Removal Paint
How To Removal Paint When repainting a part,prior to application of the new paint coat the old,paint often must be removed. The waste reduction assessment should start by examining what causes the need for repainting: inadequate initial part preparation; defects in coating application; equipment problems; or coating damage due to improper handling. While no process is perfect, reducing the need for repainting has a direct effect on the volume of waste generated from paint removal. Once the need for paintRead More …
Kinds of Phosphate Treatment for Powder Coating
Kinds of Phosphate treatment for powder coating Iron phosphate Treatment with iron phosphate (often called thin layer phosphating) provides very good adhesion properties and has no adverse effects in the mechanical properties of the powder coating. Iron phosphate provides good corrosion protection for exposure in the low and middle corrosion classes, though it cannot compete with zinc phosphate in this respect. Iron phosphate can be used in either spray or dip facilities. The number of steps in the process mayRead More …
Chromate coating for aluminium surface
Aluminium and aluminium alloys are treated by a corrosion resistant conversion coating that is called “chromate coating” or “chromating”. General method is to clean the aluminium surface and then apply an acidic chromium composition on that clean surface. Chromium conversion coatings are highly corrosion resistant and provide excellent retention of subsequent coatings. Different type of subsequent coatings can be applied to the chromate conversion coating to produce an acceptable surface. What we call as phosphating to steel an iron isRead More …
Requirements for powder coating over hot dip galvanizing
The following specification is recommended: Use zinc phosphate pretreatment if highest adhesion is required. Surface must be perfectly clean. Zinc phosphate has no detergent action and will not remove oil or soil. Use iron phosphate if standard performance is required. Iron phosphate has a slight detergent action and will remove small amounts of surface contamination. Best used for pre-galvanized products. Pre-heat work prior to powder application. Use ‘degassing’ grade polyester powder coating only . Check for correct curing by solventRead More …
Phosphating conversion coatings
The recognized pre-treatment for steel substrates just prior to application of powder coatings is phosphating which can vary in coating weight. The greater the conversion coating weight the greater the degree of corrosion resistance achieved; the lower the coating weight the better the mechanical properties. It is therefore necessary to select a compromise between mechanical properties and corrosion resistance. High phosphate coating weights can give trouble with powder coatings in that crystal fracture can occur when the coating is subjectedRead More …