What does rust converter cost? — Canada

Heavily pitted or scaled metal soaks up more product — plan for a second coat and roughly 30% more than the flat-surface figure. Rough cast iron behaves the same way.

Conversely, light surface bloom on smooth steel can stretch past the stated coverage, because you only need a thin film for the reaction to complete.

Rust converters are sold in wildly different container sizes, at wildly different solids contents, with coverage claims that are almost always quoted for a single thin coat on smooth steel. That combination makes shelf price close to meaningless. A cheap quart that only covers 30 sq ft properly and needs a separate primer afterwards costs more per finished job than a dearer bottle that primes as it converts.

The number that survives comparison is cost per treated square foot, calculated on two coats, because two coats is what pitted or salted steel actually needs. Take the price, divide by the honest two-coat coverage, and then add anything else the job forces you to buy — primer, thinners, extra abrasive discs, a second trip out for more product.

Do that arithmetic on a typical trailer frame or set of railings and the ranking usually inverts. The product that looked expensive on the shelf finishes the job in one purchase, and the bargain quart turns into two quarts plus a can of primer plus an extra Saturday.

A set of garden railings roughly 40 ft long and 3 ft high is about 120 sq ft of surface once you allow for both faces of flat bar. That is three bottles at $42 with free shipping, plus a wire brush and a topcoat you probably already own. Two afternoons of work and the ironwork is stabilised and painted for well under $60 all in.

A single-axle trailer frame with a deck is closer to 90 sq ft of treatable steel, so two bottles at $34 covers it with a little in reserve for the spring hangers and the coupling. A light-truck chassis is 150 to 250 sq ft depending on cab and bed length, which puts it in the 5-pack at $55 — around 20 cents a square foot to stop the corrosion that would otherwise write the vehicle off.

Compare that to the alternative. Media blasting a truck chassis is a few hundred dollars before anyone paints anything. A workshop rust repair on two rear arches is usually more than the entire 8-pack. The chemistry is the cheap part of rust control; the expensive part is leaving it another two winters.

Deep pitting drinks product. Pitted steel has far more true surface area than its measured dimensions suggest, and the liquid wicks into every void, which is exactly what makes it work. Budget 20 to 30 per cent above your measured area on anything heavily pitted or salted.

Rough surfaces do the same. Cast iron, weathered angle iron, corrugated sheet and old weld seams all take more than smooth panel steel. Spraying rather than brushing costs more again — overspray and atomisation loss typically add 20 to 40 per cent to consumption on open frameworks.

Prices on this site are in USD and include no hidden handling charge. Shipping is free from three bottles up; single and double packs carry a small flat rate shown before you pay. There is no subscription, no upsell after purchase, and 30 days to send back anything unopened.