Alloy Selection and Passivation Contractor in Washington

Yes, across Seattle, Tacoma, Spokane, Yakima, the Tri-Cities, the coast and statewide: alloy selection advice, in-place and shop passivation per ASTM A967 after cleaning per ASTM A380, weld heat tint removal, corrosion investigation, and fabrication in higher alloys with procedures matched to the material.

Because chloride attack is local rather than general. A chloride ion penetrates the passive film and initiates a pit whose internal chemistry becomes self-sustaining and more aggressive as it deepens, so the pit accelerates rather than stabilizing. A vessel can have an almost perfect surface and a hole through it.

Because a stagnant solution in a crevice develops a chemistry different from the bulk, and attack begins at chloride levels far below what the open surface would tolerate. Under a gasket, in a lap joint or beneath a deposit is where most real failures start, which makes geometry as important as concentration.

It combines chromium, molybdenum and nitrogen content into a single figure for ranking candidate alloys. Type 316 typically sits in the mid twenties, duplex 2205 in the mid thirties, and super duplex and 6-moly grades in the low to mid forties. It is an approximation and a genuinely useful one for selection.

Significantly. Chloride attack becomes markedly more likely as temperature rises, so an alloy that performs well in a cold brine line can fail in the same brine heated. A specification stating chloride concentration without stating temperature has not stated the duty.

No, and it carries its own risk. Duplex grades are unforgiving of welding practice because their properties depend on a phase balance affected by heat input and cooling rate. Super duplex welded as though it were 316 can end up performing worse than the 316 it replaced.

No. It restores the passive film and removes free iron, both of which are essential, but it cannot raise an alloy’s inherent resistance. Passivating 316 in a duty that requires super duplex gives you a properly passivated 316 component that will still pit, on a slightly longer timescale.

More so, not less. Welding leaves chromium-depleted heat tint that is the preferred initiation site for chloride attack. A plant that has paid for super duplex and left heat tint in place has spent the money and kept the failure mode, which is the worst of both outcomes.

Every cut and reweld reintroduces heat tint and potentially embedded iron from carbon steel tooling. In marine or brine service that repair becomes the next pit unless it is cleaned and passivated afterwards, which makes post-repair treatment part of the maintenance procedure rather than an optional extra.

Use the form on this page or call 201-450-8280. Useful inputs are the fluid and its chloride content, the operating temperature, current material and how long it has lasted, where failures appear, and whether the item is new fabrication or a replacement.

The chemistry and verification are similar, but duplex's two-phase structure and its sensitivity to heat tint mean that tint removal after welding is more critical and that some test methods respond differently. The procedure is qualified on the duplex grade rather than transferred from 316.

Super duplex and super austenitic grades with high molybdenum and nitrogen for most duties, and nickel-based alloys or titanium for the most severe. 316 is used in cold, well-flushed seawater with a short life expectation, and rarely in brine.

Titanium for most seawater duties, copper-nickel where biofouling is the larger problem, and super duplex or 6% molybdenum stainless where the exchanger's other side sets the material, because 316 tubes pit in seawater at any temperature. Exchanger tubes are the most seawater-exposed surfaces in a plant.

On seawater pumps, intake structures, heat exchanger water boxes and mixed-metal piping, using sacrificial anodes or impressed current, to protect the less noble metal where galvanic couples cannot be avoided. It complements alloy selection rather than replacing it.

With chlorination or other biocide at the intake, velocity that discourages settlement, and cleaning and inspection at low-flow points, because fouling reduces flow and creates the crevices and deposits where corrosion starts. Fouling control is a corrosion control.

An over-alloyed filler with higher molybdenum and nickel than the base metal, so that the weld metal's pitting resistance matches or exceeds the parent's after the dilution and segregation of welding. Welds made with matching filler pit before the plate.

At crevices, welds, under deposits and at the waterline, where chloride attack initiates, on an interval set by the alloy and the duty. Visual inspection of the general surface misses the damage.

Cold saturated brine is a demanding chloride duty, and equipment in it needs an alloy selected for it, fresh water rinsing when idle, and passivation after cleaning. Brine tanks and chillers are a common failure location.

Salt deposition attacks exposed stainless, especially sheltered surfaces that rain does not wash, and fresh water washing removes it. Coastal plants include external washing in maintenance.

By the location and form of the attack, deposit and microbiological analysis, and metallography of the pit morphology, which show whether the attack started at a crevice, under a deposit or on an open surface. The mechanism determines whether the fix is design, alloy or chemistry.

Different alloys in contact in seawater form galvanic cells, and mixed-alloy systems fail at the less noble metal. Alloy consistency and isolation at joints are designed in.

Neutralised and discharged under the plant's permit, which for coastal and marine sites often has strict limits. The route is confirmed before treatment.

Inland plants using brine or high-chloride water see the same mechanism without the marine atmosphere. The chloride in the fluid is what matters.

By the chloride and temperature at the failure against the alloy's capability. Failure within the alloy's capability points to a surface or fabrication issue that passivation and repair fix; failure beyond it is a materials issue.

316 in brine or seawater failing at crevices and welds, repeatedly repaired in 316, with each repair failing sooner. The alloy is the answer.

No. Passivation restores the surface an alloy is capable of and cannot add the molybdenum that gives 316 its chloride resistance. Citric passivation on 304 in brine service is worth doing and will not save it. Where the duty is genuinely chloride-heavy, the honest answer is a material change rather than a surface treatment.

On correctly specified equipment after fabrication, welding or repair, where embedded iron and heat tint would otherwise be the first place a pit starts. Citric passivation in place, with rinse water whose chloride content has been checked, is the standard treatment and the rinse water is the part most often overlooked.