Technical Reference

Treatment Procedures.

Step-by-step waterproofing, structural repair and rehabilitation methods, grouped by the chemistry they use, each mapped to the Armstrong products that carry it out. Select a treatment to view the full procedure and product recommendations.

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Treatment · Corrosion protection

Steel & Rebar Corrosion Protection

Clean back to firm steel, convert what remains, prime with zinc

Applications

Structural steel and shedsGates, grills and railingsMetal sheet roofsPipelines and tanksExposed reinforcement in concrete

Procedure

Remove everything loose with a wire brush, emery paper or a grinder with a wire cup: flaking paint, mill scale and loose rust, until the steel is firm. On rebar, chip the concrete back behind the bar so it can be cleaned all round.
Blow off the dust. Keep the steel dry from here on; no washing.
Where tight rust still holds in pits and cannot be brushed out, brush ALSTRONG RC straight onto it. It converts the rust in about 30 minutes and needs no rinsing; give heavily rusted areas a second coat.
Prime the same day, before fresh rust forms. Structural steel and sheets: one coat of ALSTRONG ZP 777 at 25 to 35 microns, or two coats of ALSTRONG ZP PRIMER 210 where the steel can be blast-cleaned. Rebar in concrete: two coats of ALSTRONG AC within 3 to 4 hours of cleaning.
Do not prime in rain or heavy humidity: keep humidity below 85% and the steel at least 3°C above dew point for ALSTRONG ZP 777.
Topcoat after at least 12 hours at 30°C. On rebar, the bond coat and repair mortar go on once the coating is dry.

Important Suggestions

ALSTRONG RR-170 is an acid rust remover that has to be rinsed off and dried, so it is used on loose items that can be dipped or brushed and washed, such as bolts, fittings and machinery parts, not on rebar inside concrete or on steel on site. ALSTRONG ZP 777 is flammable; keep away from flames and ventilate confined areas.

Why This Treatment?

Zinc protects steel sacrificially: it corrodes in place of the steel. Brushing back to firm steel and converting the rust that is left means the primer holds on sound metal, so the rust does not come back under new paint or repair mortar.