POWER PLANT:SURFACE PREPARATION

POWER PLANT

SURFACE PREPARATION:

The life of a coating system depends primarily on surface preparation. Therefore, the Contractor should precisely follow the degree of specified surface preparation in this specification.

Steel:

The surface preparation of this specification is governed by the Swedish Standard SIS 055900 or equivalent international standards.

Reference to surface preparation grades is indicated below:

Surface Preparation Grades:

-           SA 1 - SP 7 No. 4:           light blast cleaning
-           SA 2 - Grade 3 SP 6 No. 3:           thorough blast cleaning
-           SA 2.5 - Grade 2 SP10 No. 2:           very thorough blast cleaning
-           SA 3 - Grade 1 SP 5 No. 1:           blast cleaning to pure metal

The abrasives used for blast cleaning shall be grit, shot, graded flit or silica sand (where allowed) and shall be such that they will produce an average anchor pattern of 25-50 microns.

After blast cleaning all accumulated blasting material, dust, etc. must be removed, leaving a surface, which is clean, dry and free of mill scale, rust, grease, and other contaminants.

The blasted steel shall be primed, as specified in the specifications, immediately after blasting and cleaning to avoid rusting.

Before field touch-up, all surfaces to be touched up, such as boltings, weldings and unprimed plates shall be cleaned from all rust, scale, welding contaminants, grease, oil, and other foreign matters. Damaged primer shall be removed from welded or defective areas until the sound primer is encountered.

Surfaces, which have been coated, but are not meeting the standards of this specification shall be reblasted and coated at the Contractor's cost.

Concrete:

New concrete and masonry shall not be painted for at least 28 days to permit the concrete and mortar to cure and dry out.
All dirt, loose material, and latency are to be removed by wire brushing or stone rubbing.

All holes and rough spots shall be patched with an acceptable filler material as per the manufacturer's recommendation.

Galvanizing:

Galvanized surfaces should be solvent-cleaned to remove oil.

 After that, the surface shall be etched in accordance with the manufacturer's recommendation.

For surfaces where galvanizing is specified, all galvanizing shall be carried out by the hot-dip process, and unless otherwise specified shall conform in all respects to BS 729 or equivalent.

 The detailed design of members shall be in accordance with BS 4479 or equivalent.

Wood:

No paint or stain shall be applied to unfinished wood has a moisture content of more than 8%.
When required, wood surfaces should be alkaline cleaned to remove any grease, oil, or wax.

 Alkalinity on the surface should be removed with water-soaked wipers and then be dried. The surface should be smoothed by fine sanding.

Application of paint or stain should be done in accordance with the manufacturer's recommendation.