AS NZS 3750.9:2009 pdf free download – Paints for steel structures
B4 TYPICAL USES
Organic zinc-rich primers are generally used in the protection of iron and steel exposed to industrial and marine environments and are typically topcoated with paints such as acrylics, epoxies and polyurethanes. They are also used to repair or maintain weathered or damaged zinc-rich coatings or galvanized surfaces and in areas where size or geometry precluded spray application of inorganic zinc rich coating. Organic zinc-rich primers are often considered as alternatives to inorganic zinc-rich primers in situations where ease of application is of more importance than galvanic protection and damage resistance. When compared to inorganic zinc-rich primers these coatings may be applied and cured under a wider range of atmospheric conditions and may be more tolerant to lower grades of preparation for steel surfaces. They are easier to overcoat than inorganic zinc-rich coatings because of their non-porous nature.
B5.1 Type 1 products
Type 1 products may be single-pack based on resinous materials such as styrenes, acrylics, chlorinated rubbers, chlorinated rubbers, epoxy esters and moisture cure urethanes that harden on air-drying. A significant advantage of Type 1 products over Type 2 products is that there is no mixing of components required before use. Hence there are no wastage or pot-life issues. Ease of application makes these products popular with applicators in maintenance situations. In these situations where abrasive blast cleaning is not practicable, Type 1 products may provide an acceptable level of performance over less well prepared surfaces. Type 1 products require special consideration to ensure that they are topcoated with a compatible paint. In some situations a barrier coat may be required between Type 1 primers and subsequent coats. Unless they area known to be compatible, Type 1 products should not be topcoated with multi-component paints. Manufacturers should be consulted to ensure that all coatings within the system are compatible. The maximum service temperature recommended for Type 1 products is 65°C.
B5.2 Type 2 products
Type 2 products are two-pack materials that harden by the chemical reaction of the components. Such materials are commonly based on epoxy resins. These products perform best over well prepared surfaces, particularly over surfaces abrasive blast cleaned to a minimum of Class 2½ (AS 1627.4). Type 2 products may be used in maintenance situations and are often used as an alternative to inorganic zinc-rich primers in shop and field applications. Type 2 products may be used with a wide range of intermediate and finish coats, and manufacturers should be consulted as to recommended coating systems. Ambient temperatures in excess of 12°C are necessary to affect satisfactory curing of conventional epoxies. However, low temperature curing versions are available that allow curing at temperatures as low as 5°C. The maximum service temperature recommended for Type 2 products is 200°C.
No attempt should be made to extend the pot-life of Type 2 products beyond that stated by the manufacturer. The addition of solvent or blending with freshly mixed product usually results in unsatisfactory coatings. Any unused mixed product that has reached its stated pot- life should therefore be discarded.