Code of practice for the painting of ferrous metals in buildings, Part 2: Painting
1971 Edition

IS 1477 Part 2 (1971) prescribes specific coating schedules for ferrous metals inside and outside buildings. For interiors, full gloss enamel finishes require two coats of red lead primer (IS 102-1962, IS 2074-1962), followed by an undercoat (IS 133-1965 or IS 2933-1964) and two finishing coats of the same undercoat paint, totaling at least 100 microns thickness. Oil gloss, eggshell gloss, flat finishes, metallic, and bitumen coatings have their respective primer and finishing paint specifications detailed similarly. Exterior schedules adjust undercoats and finishing coats with standards such as IS 2933 and IS 2932, maintaining the same total film thickness and primer requirements.

The standard specifies that surface preparation includes mechanical or chemical removal of rust and scale through methods like wire brushing, scraping, sandpapering, power tooling, flame cleaning, sandblasting, or pickling as outlined in IS 1477 Part I. Immediately after cleaning, especially in humid or coastal environments, the first primer coat must be applied without delay to prevent contamination. After the second primer coat dries, lightly abrade the surface to ensure adhesion, then thoroughly clean off all dust before applying subsequent coats.

Primers should be applied promptly following surface cleaning to prevent contamination, preferably by brushing for better adhesion, particularly avoiding spray application for lead-based primers. Recommended primer types include red lead non-setting, zinc chrome, and red oxide-zinc chrome variants as per IS specifications. Fillers must be factory-produced and compatible with primers and paints; on-site mixtures such as whiting with linseed oil are discouraged due to incompatibility. For best results, all paint layers—primer, filler, undercoat, and finishing coats—should be sourced from the same manufacturer to ensure chemical harmony and avoid surface defects like cracking or wrinkling.

For spray application, maintain the spray gun perpendicular to the surface and employ a steady, uniform sweeping motion at a distance of 150–250 mm, adjusting air pressure and fan to optimize coverage and minimize waste. Release the trigger before completing each stroke and clean spray components frequently to avoid defects. For brush painting, hold the brush at roughly a 45-degree angle to the surface, use several light strokes to transfer paint, rotate the brush 180 degrees to use both sides of bristles, and apply paint with vertical strokes followed by cross-wise strokes, finishing with vertical strokes to ensure an even, streak-free finish.

The code advises cautious use of chemical paint removers: alkali-based removers may damage nearby materials if not thoroughly rinsed, and solvent-based removers involve fume and fire risks and require complete wax residue removal to ensure proper adhesion. Mechanical removal by scraping and chipping is preferred for safety and effectiveness. Prior to repainting, inspect the existing coating condition to determine whether full removal is necessary or if repainting over the old paint is acceptable, following appropriate surface cleaning and preparation.