powder coating pretreatment
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Difference between cold rolled steel and hot rolled steel
COLD ROLLED STEEL:The most common of the metals encountered by the jobshop powdercoater, this product is roll formed to a close tolerance and a fine surface finish, suitable for stamping, forming, and moderate drawing operations. This material can be bent flat upon itself without cracking. Good base for phosphate conversion coating. Pretreatment recommendations are Clean, Phosphate, rinse, and seal or deionize rinse. HOT ROLLED STEEL:A low carbon steel suitable for forming, punching, welding, and shallow drawing. Surface has normal millRead More …
Alkaline Cleaning for substrate
Alkaline cleaners are the most common method of soil removal for metal preparation prior to the application of powder coatings. Cleaners based on sodium hydroxide (caustic) are very economical where cleaning by saponification is desirable. Caustic cleaning media are highly reactive on non-ferrous surfaces and they can cause over-etching on aluminum and zinc surfaces, possibly creating smut and adding zinc to the solution. Caustic cleaning residues are also difficult to rinse away, especially if the solution temperature is in the high range. Alkali silicatesRead 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 …
The solutions for the problems of powder coating over hot dip galvanizing
1. Incomplete curing: Polyester powder coating powder is thermosetting resins that cross-link to their final organic form by being maintained at a temperature (typically 180 o C), for about 10 minutes. Curing ovens are designed to provide this time at temperature combination. With hot dip galvanized items, with their heavier section thickness, it is necessary to ensure that sufficient stoving time is allowed to meet the curing specifications. Pre-heating of the heavier work will assist in accelerating the curing processRead More …
The problems with powder coating application over galvanized surface
Polyester powder coating over hot dip galvanized steel provides a high grade architectural finish to steel items with excellent atmospheric weathering characteristics.The powder coated product ensures maximum durability for steel components, which will generally provide 50 year+ rust free life spans in most architectural applications. Even so there are still some problems during this application. Hot dip galvanized surfaces have been acknowledged as difficult to powder coating since the technology was first developed in the 1960’s. Industrial Galvanizers commenced research inRead 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 subjected to locallyRead More …
Various Substrates for Powder Coating
Substrates Aluminium,steel,zinc alloys,copper and galvanized steel are common metals on which powder coatings are applied. In a number of cases where normal service conditions apply, satisfactory properties can be obtained on thoroughly cleaned metal. Aluminium For aluminium and its alloys,performance can be upgraded using a proprietary chromate conversion coating, even though the clean surfaces are easily coated and adhesion is excellent Steel For iron/steel surfaces maximum corrosion and salt spray resistance are given by a zinc phosphate conversion coating. Zinc alloys With allRead More …
Main aims in the pretreatment to metal surface before coating
The main aims in the preparation of a metal surface before powder coating may be defined as follows: The conditioning of the surface so as to render it suitable for the coating that is to be applied The complete removal of all foreign matte,e.g,scale,grease,cutting oil,soil,welding splatter,etc The pretreatment should impart uniformity throughout all treated workpiece surfaces,irrespective of the source of the metal or of the contaminants that might adhere. As with other methods of organic finishing attention to the pretreatment stage isRead More …
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