Dakromet bilan qoplangan murvat va yong'oqlar 

This article explains the fastener families involved, the corrosion mechanisms that attack threaded joints, why Dacromet suits bolts and nuts alike, and how to specify and assemble a matched bolt-nut-washer set.

2. Korroziya tishli bo'g'inga qanday hujum qiladi

Threads are the most corrosion-vulnerable geometry on any fastener assembly:

1.Crevice corrosion— the microscopic gap between bolt thread flank and nut thread flank traps moisture and electrolyte, creating an oxygen-starved crevice where anodic sites form and pitting begins;

2.Galvanik korroziya— dissimilar coatings or metals (a Dacromet bolt with an electro-plated nut, a stainless bolt in a galvanized nut) drive preferential corrosion of the less noble component;

3.Yig'ishda qoplamaning shikastlanishi— qisish paytida iplar qirib tashlanadi va o'tlanadi; thin electroplate and organic paints are easily cut through, exposing bare steel in the thread roots;

4.Stress concentration— the first load-bearing thread carries a disproportionate share of preload, so corrosion pits there rapidly become fatigue cracks;

5.Tebranish ostida tirnash xususiyati— micro-movement between bearing faces abrades the film, inviting white rust and then red rust.

Once rust products build up in the threads, the nut seizes, disassembly torque exceeds installation torque, and the bolt or stud often has to be cut out — the classic "frozen nut" failure in field maintenance.

3. Moslashtirilgan to'plamning korroziyaga chidamliligi

Table 1. Coating systems for bolt-nut assemblies compared (typical industry values).

Because the coating is applied to finished, heat-treated parts and cured below the tempering temperature, both bolts and nuts keep their full mechanical properties — tensile strength, proof load and hardness per ISO 898-1 / ISO 898-2 — unchanged.

4. Assambleyaning eng yaxshi amaliyotlari

1.Hech qachon qoplama tizimlarini aralashtirmang— pair Dacromet bolts only with Dacromet nuts and washers; a mixed couple drives galvanic corrosion of the weaker (usually zinc-plated) part;

2.Moment jadvalini hurmat qiling— lubricated Dacromet pairs have a lower, more stable nut factor than bare steel; reusing old torque values over-tightens and may strip the nut threads;

3.Do not re-lubricate— the integrated topcoat already sets the friction coefficient; additional oil on threads changes K unpredictably;

4.Mind the jam-nut order— when a thin nut and a full nut are stacked (classic locking arrangement), tighten the full nut against the thin nut;

5.Watch for gallingon stainless pairs — Dacromet's lubricant topcoat also reduces galling risk on stainless studs;

6.Birinchi maqola moment-kuchlanishni tekshiringon a testing skid, using the actual bolt-nut-washer combination from the production lot.

5. Xulosa

Corrosion failure rarely starts on the shank of a bolt — it starts in the threads, in the crevice between the bolt and the nut. Bardoshli bo'g'in shuning uchun talab qiladi mos keladigan korroziyadan himoya paketi: Dacromet-coated bolts, nuts and washers in the same zinc-flake system, specified together (ISO 10683 / ASTM F1136, flZn 8/10, ≥ 720 h NSS), assembled with the correct torque and friction values. The result is a threaded connection that resists white rust, red rust, pitting, crevice attack and seizure — through years of salt spray, weather and vibration.