The scope of this guide covers the surface preparation of metallic surfaces for the subsequent application of paint and metal coatings for corrosion protection or the enhancement of surface appearance for the both new structure and maintenance treatments.
Organic paint coatings adhere to the surface mainly by polar adhesion important for thick coating films. For all types of coatings, the surface condition of the substrate is critical in terms of coating performance and durability.
The life & performance of any paint system depends directly upon surface preparation. About 60% of all coating failures are due to improper surface treatment. Therefore, it is of vital importance to fully comprehend this aspect of painting.
Method For Steel Surface Preparation
To remove oil, grease &other contaminations apply solvent/degreaser to wash the surface, followed by wiping dry with clean cloth.
Loose rust, mill scale & old paint can be removed by hand or power tools such as power wire brush & grinders are more effective than hand tools.
Is alternative method for scraping & wire brushing & is used where the area of treatment is small. Both manual & mechanical (Sanders)can be used
A high-speed water jet can also be used for removing rust, loose paint, chemical contaminants, grease etc. High-pressure water blasting can also be carried out by using hot water & / or special cleaning agents.
Rust & mill scale can be removed by acid & / or chemical pickling. Recommended for in – shop treatment, not advisable for on-site work.
It is the most effective method of cleaning steel. It is recommended for removal of mill scale, heavy rust, rust – scale & previous coating from extensive prior to sand blasting it is essential to first degrease the steel. Generally four grades can be achieved by abrasive blasting to the Swedish standard or British Standard, that is, as below:
- Light blast cleaning GR SA – 1
- Through blast cleaning GR SA–2 / BS 4232 3rd quality
- Very thorough blast cleaning GR SA-2.5 BS 4232 2nd quality
- Blast cleaning to white metal GR SA-3 /BS 4232 1ST quality
Paint Stripper (paint remover); Flame cleaning (burning off mill scale,rust, old paint etc); Alkaline cleaning etc.
- Swedish Standard: SIS 055900
- British Standard: 4232