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High Strength Low Alloy (HSLA) Corrosion

Carbon steel can be alloyed, singly or in combination, with chromium, nickel, copper, molybdenum, phosphorus, and vanadium in the range of a few percent or less to produce high strength low-alloy (HSLA) steels. In some circumstances, the addition of 0.3% copper to carbon steel can reduce the rate of rusting by one quarter or even by one half. A modern and comprehensive document on the subject is the second edition of the classic CORROSION BASICS textbook.

Typically, HSLA steels are low-carbon steels with up to 1.5% manganese, strengthened by small additions of elements, such as columbium, copper, vanadium or titanium and sometimes by special rolling and cooling techniques. Improved-formability HSLA steels contain additions such as zirconium, calcium, or rare-earth elements for sulfide-inclusion shape control. The higher alloy additions are usually for better mechanical properties and hardenability.

Because HSLA alloys are stronger, they can be used in thinner sections, making them particularly attractive for transportation-equipment components where weight reduction is important. The lower range of about 2% total maximum is of greater interest from the corrosion standpoint. Strengths are appreciably higher than those of plain carbon steel, but the most important attribute is a better resistance to atmospheric corrosion when freely exposed.

HSLA Steel is a type of steel alloys that provide many benefits over regular steel alloys. In general they are much stronger and tougher than ordinary carbon based steel. It is used in cars, trucks, cranes, bridges and other structures that must be able to handle a lot of strain. HSLA Steel only contain a very small percentage of carbon, less than one percent, and only small amounts of other added metals.

Stress corrosion cracking (SCC) of HSLA steel

All steels are affected by hydrogen, as is evidenced by the influence of hydrogen on corrosion fatigue crack growth, and the occurrence of hydrogen-induced cracking 5 under the influence of very high hydrogen concentrations. However, hydrogen embrittlement under static load is only experienced in steels of relatively high strength. (reference)

There is no hard-and-fast limit for the strength level above which problems will be experienced, as this will be a function of the amount of hydrogen in the steel, the applied stress, the severity of the stress concentration and the composition and microstructure of the steel. As a rough guide hydrogen embrittlement is unlikely for modern steels with yield strengths below 600 MPa, and is likely to become a major problem above 1000 MPa. The hydrogen may be introduced into the steel by a number of routes, including welding, pickling, electroplating, exposure to hydrogen-containing gases and corrosion in service. The effects of hydrogen introduced into components prior to service may be reduced by baking for a few hours at around 200 C. this allows some of the hydrogen to diffuse out of the steel while another fraction becomes bound to relatively harmless sites in the microstructure.

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See also:Equilibrium reactions of iron in water, Iron corrosion products, Iron species and their thermodynamic data, Pourbaix diagram of iron, Rust chemistry, Rust converters, Steel corrosion

Or: Aluminum, Aluminum alloys, Brass, Bronze, Cadmium, Chromium, Cobalt, Copper, Gold, Iron, Lead, Magnesium, Molybdenum, Nickel, Nickel alloys, Silver, Stainless steels, Steel, Tantalum, Tin, Titanium, Zinc, Weathering steel